System Design Chapter 1 Quiz
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Questions and Answers

What is essential to ensure the smooth implementation of large scale software systems?

  • Writing code without design considerations
  • Avoiding user requirements analysis
  • First principles thinking in technical architecture (correct)
  • Focusing solely on algorithms and data structures

    • What do large enterprises need to carefully evaluate when designing software systems?

  • The latest programming languages
  • Trade-offs and user access patterns (correct)
  • Internal company politics
  • Social media trends

    • Why is understanding business requirements important in system design?

  • It reduces the need for error handling
  • It aligns the system with customer needs (correct)
  • It helps in feature bloat
  • It allows for faster coding without planning

    • What can enterprises avoid by investing time in understanding bottlenecks?

    <p>Inefficient software development efforts</p> Signup and view all the answers

    In the context of system design, what should be considered along with algorithms and data structures?

    <p>Futuristic changes and robustness</p> Signup and view all the answers

    What is a consequence of failing to properly design a large scale software system from the beginning?

    <p>Wasted software development efforts</p> Signup and view all the answers

    What is emphasized as a key aspect of designing technical architecture in system design?

    <p>Comprehensively evaluating systems</p> Signup and view all the answers

    Which of the following plays a critical role in the design phase of software development?

    <p>Understanding user objectives</p> Signup and view all the answers

    What is the main goal of understanding system design concepts?

    <p>To help with building large-scale software systems</p> Signup and view all the answers

    Which of the following statements best describes asynchronous communication?

    <p>It can happen without waiting for a reply.</p> Signup and view all the answers

    Which characteristic applies to synchronous communication?

    <p>It prevents further action until a response is received.</p> Signup and view all the answers

    In system design, what does consistency refer to?

    <p>The same data being viewed across all replica nodes at a given time.</p> Signup and view all the answers

    What is a primary benefit of asynchronous communication in system design?

    <p>It provides flexibility and tolerance for delays.</p> Signup and view all the answers

    Which aspect is NOT one of the fundamental concepts of system design?

    <p>Data warehousing</p> Signup and view all the answers

    When is synchronous communication typically preferred?

    <p>When real-time response is needed.</p> Signup and view all the answers

    What challenges are associated with consistency in distributed systems?

    <p>Keeping multiple replica nodes in sync with updates</p> Signup and view all the answers

    What is a common requirement for consistency regarding data storage and retrieval?

    <p>Each read must return the most recent value.</p> Signup and view all the answers

    Which scenario exemplifies asynchronous communication?

    <p>Email communication with a follow-up if no reply is received.</p> Signup and view all the answers

    What is a key characteristic of large-scale software systems?

    <p>They integrate multiple small sub-systems.</p> Signup and view all the answers

    In system design, what does fault tolerance refer to?

    <p>The capability to continue functioning despite failures.</p> Signup and view all the answers

    What is the purpose of using abstraction in system design?

    <p>To simplify and model complex system details.</p> Signup and view all the answers

    What is typically a consideration when deciding between synchronous and asynchronous communication?

    <p>Specific requirements and constraints of the system</p> Signup and view all the answers

    What is the primary purpose of redundancy in system availability?

    <p>To maintain functionality during a component failure</p> Signup and view all the answers

    What is a key characteristic of fault tolerance in a system?

    <p>It allows a system to operate despite errors or failures</p> Signup and view all the answers

    How does load balancing contribute to system availability?

    <p>By redistributing requests among multiple servers</p> Signup and view all the answers

    Which type of failover pattern involves multiple systems processing requests in parallel?

    <p>Active-active</p> Signup and view all the answers

    What is a potential drawback of an active-passive failover system?

    <p>Reduced availability during primary system failure</p> Signup and view all the answers

    In a multi leader replication pattern, what is a challenge that arises?

    <p>Conflicts and synchronization issues increase</p> Signup and view all the answers

    What is the main function of a single leader replication pattern?

    <p>To have one leader responsible for updates and followers for reads</p> Signup and view all the answers

    What happens if the leader system in a single leader replication pattern fails?

    <p>Data updates may be lost if not replicated</p> Signup and view all the answers

    Which of the following best describes the purpose of failover patterns?

    <p>To ensure continuous operation in case of a failure</p> Signup and view all the answers

    What is a common risk associated with both failover and replication patterns?

    <p>Complexity in implementation and management</p> Signup and view all the answers

    What is a major advantage of using multi leader replication over single leader replication?

    <p>Increased flexibility to read and write data</p> Signup and view all the answers

    Which approach effectively limits the risk of data loss in a failover system?

    <p>Implementing timely updates to followers</p> Signup and view all the answers

    What defines the active-active failover pattern?

    <p>All systems actively participate in processing</p> Signup and view all the answers

    Which aspect is crucial when choosing a failover pattern?

    <p>The desired level of availability and implementation costs</p> Signup and view all the answers

    What is the primary goal of data replication in distributed systems?

    <p>To maintain multiple copies of data across replica nodes.</p> Signup and view all the answers

    Which of these techniques helps recover data consistency after a system crash?

    <p>Write-ahead logging</p> Signup and view all the answers

    What does monotonic read consistency guarantee?

    <p>A client will never see outdated data on subsequent reads.</p> Signup and view all the answers

    Which consistency model guarantees that updates are immediately reflected across all replica nodes?

    <p>Strong consistency</p> Signup and view all the answers

    In which scenario would conflict resolution be necessary?

    <p>When two replica nodes attempt to update the same data at the same time.</p> Signup and view all the answers

    What role do consensus protocols play in distributed systems?

    <p>They ensure all nodes agree on updates to the data.</p> Signup and view all the answers

    Which technique involves assigning version numbers to write operations?

    <p>Data versioning</p> Signup and view all the answers

    What is a key characteristic of causal consistency?

    <p>It maintains the order of causally-related operations.</p> Signup and view all the answers

    What is the purpose of locking mechanisms in data storage systems?

    <p>To prevent multiple write operations from interfering with each other.</p> Signup and view all the answers

    Which of the following describes eventual consistency?

    <p>Updates may take time to be visible across all nodes.</p> Signup and view all the answers

    What is the impact of failures or delays in distributed systems?

    <p>They prevent data consistency across replica nodes.</p> Signup and view all the answers

    How does monotonic write consistency affect subsequent reads?

    <p>They will consistently reflect the latest acknowledged writes.</p> Signup and view all the answers

    What does the consistency spectrum model illustrate?

    <p>It describes different consistency guarantees in distributed systems.</p> Signup and view all the answers

    What is a common challenge in achieving strong consistency?

    <p>It requires all nodes to communicate simultaneously.</p> Signup and view all the answers

    What is a primary consequence of using multiple read replicas in a system?

    <p>Increased replication lag</p> Signup and view all the answers

    What typically limits the performance of read replicas compared to the leader system?

    <p>Leader systems execute writes in parallel</p> Signup and view all the answers

    Which metric is used to measure the average time a system can operate without failure?

    <p>Mean time between failures (MTBF)</p> Signup and view all the answers

    What does a low mean time to repair (MTTR) indicate about a system?

    <p>The system can be restored to operation quickly</p> Signup and view all the answers

    Which fallacy is associated with the assumption that network outages and packet losses are negligible?

    <p>Reliable Network</p> Signup and view all the answers

    How can reliability and availability be described in the context of system design?

    <p>Both can exist at high levels or be low simultaneously.</p> Signup and view all the answers

    What is vertical scaling primarily concerned with?

    <p>Increasing the resources of a single server</p> Signup and view all the answers

    What must be accounted for when designing systems to manage the inherent limitations of network data transfer speeds?

    <p>Latency</p> Signup and view all the answers

    Which fallacy refers to underestimating the security risks inherent in a distributed network?

    <p>Secure Network</p> Signup and view all the answers

    Which type of scaling is generally more cost-effective for unpredictable traffic patterns?

    <p>Horizontal scaling</p> Signup and view all the answers

    What essential component can help achieve high reliability and availability in a system?

    <p>Robust failover mechanisms</p> Signup and view all the answers

    How should systems be designed in relation to changing network conditions?

    <p>Be oblivious to topology changes</p> Signup and view all the answers

    Which of the following can indicate a system's reliability?

    <p>Mean time between failures (MTBF)</p> Signup and view all the answers

    Which of the following fallacies involves misjudging the costs associated with network infrastructure?

    <p>Zero Transport Cost</p> Signup and view all the answers

    What does horizontal scaling achieve in system design?

    <p>Adds more simple servers to meet load demands</p> Signup and view all the answers

    What is a primary consequence of the assumption that a network is homogenous?

    <p>Interoperability challenges</p> Signup and view all the answers

    When designing systems, why is it critical to account for potential network failure?

    <p>To ensure fault tolerance</p> Signup and view all the answers

    What is the impact of the number of read replicas on a system's processing capabilities?

    <p>May reduce the number of reads they can process</p> Signup and view all the answers

    In which scenario is vertical scaling typically most advantageous?

    <p>When load increases are foreseeable and manageable</p> Signup and view all the answers

    Which AWS Well-Architected Framework pillar is related to managing the fallacy of a single administrator?

    <p>Operational Excellence</p> Signup and view all the answers

    What is a key strategy to mitigate the effects of finite bandwidth in network designs?

    <p>Employing lightweight data formats</p> Signup and view all the answers

    What type of replication pattern can be more efficient for writes than read replicas?

    <p>Leader system replication</p> Signup and view all the answers

    What is a defining characteristic of a system with high reliability?

    <p>Longer operational periods without failure</p> Signup and view all the answers

    Which of these fallacies highlights the misconception about external threats to data integrity?

    <p>Secure Network</p> Signup and view all the answers

    What must systems ensure concerning network traffic due to the assumption of infinite bandwidth?

    <p>Avoidance of resource contention</p> Signup and view all the answers

    What principle helps counter the impact of latency in distributed systems?

    <p>Edge computing</p> Signup and view all the answers

    How can developers effectively handle the complexity introduced by multiple administrators in large systems?

    <p>Design in a decoupled manner</p> Signup and view all the answers

    Which fallacy involves the assumption that the network configuration remains stable over time?

    <p>Fixed Topology</p> Signup and view all the answers

    What does eventual consistency guarantee in a distributed system?

    <p>Given enough time, all replica nodes will eventually have the same view of the data.</p> Signup and view all the answers

    How is availability typically quantified in a system?

    <p>As the percentage of time the system is operational over a specific period.</p> Signup and view all the answers

    What is the goal for achieving high availability typically measured in?

    <p>Nines, such as five nines.</p> Signup and view all the answers

    What happens when components with 99.9% availability are arranged in sequence?

    <p>The overall availability is calculated as the product of their individual availabilities.</p> Signup and view all the answers

    In terms of data consistency, what does strong consistency ensure?

    <p>The order of operations is preserved and visible immediately to all nodes.</p> Signup and view all the answers

    Which of the following could make achieving higher levels of availability more difficult?

    <p>Resource constraints for maintenance and redundancy.</p> Signup and view all the answers

    What is an example of a system that might strive for very high availability levels?

    <p>Financial trading platforms.</p> Signup and view all the answers

    What is the expected result of querying a node under eventual consistency before all replicas are synchronized?

    <p>The system may return stale data.</p> Signup and view all the answers

    How does parallel arrangement affect the overall availability of system components?

    <p>It increases total availability significantly.</p> Signup and view all the answers

    What happens when aiming to increase availability by adding more 'nines'?

    <p>Each additional nine demands exponential increases in resources.</p> Signup and view all the answers

    Which of the following is true about a system's availability during high load or errors?

    <p>A highly available system should process requests in a timely fashion even under such conditions.</p> Signup and view all the answers

    What is the relationship between the components arranged in a sequential system and their overall availability?

    <p>The overall availability is the product of the individual availabilities.</p> Signup and view all the answers

    What does a system designer consider when choosing a consistency model?

    <p>Trade-offs between consistency and availability.</p> Signup and view all the answers

    What is a primary advantage of horizontal scaling in managing unpredictable traffic?

    <p>It allows for cost-effective handling of increased requests.</p> Signup and view all the answers

    Which of the following aspects must be covered to ensure a software system is maintainable?

    <p>Operability, Lucidity, Modifiability</p> Signup and view all the answers

    Which feature of a distributed system ensures order preservation of updates?

    <p>Strong consistency.</p> Signup and view all the answers

    What is the main goal of fault tolerance in large-scale systems?

    <p>To ensure continuous service amid hardware or software failures.</p> Signup and view all the answers

    How does replication contribute to fault tolerance?

    <p>By duplicating nodes and data across multiple storage locations.</p> Signup and view all the answers

    What characterizes synchronous checkpointing in a system?

    <p>It necessitates halting all data mutations until completion.</p> Signup and view all the answers

    Why is modifiability important in system design?

    <p>To enable easy modifications without disrupting subsystems.</p> Signup and view all the answers

    What does lucidity in a system primarily ensure?

    <p>Ease of understanding and collaboration among team members.</p> Signup and view all the answers

    What is a disadvantage of asynchronous checkpointing?

    <p>It can lead to inconsistent data states across servers.</p> Signup and view all the answers

    Which scaling method is recommended for early-stage systems before moving to horizontal scaling?

    <p>Vertical scaling with improved configurations.</p> Signup and view all the answers

    What is a key characteristic of operability in system design?

    <p>The system should return to normal operations swiftly after faults.</p> Signup and view all the answers

    What is the primary purpose of checkpointing in large-scale systems?

    <p>To ensure data reliability and integrity.</p> Signup and view all the answers

    What is a fundamental challenge of horizontal scaling?

    <p>It complicates the management of multiple servers.</p> Signup and view all the answers

    Which technology can enhance the durability of a database during failures?

    <p>Checkpointing mechanisms</p> Signup and view all the answers

    What does fault tolerance help prevent in large-scale systems?

    <p>Loss of data due to server downtimes.</p> Signup and view all the answers

    What is crucial for the successful implementation of large scale software systems?

    <p>First principles thinking in technical architecture</p> Signup and view all the answers

    Which aspect is NOT considered when designing large scale software systems?

    <p>Peer programming techniques</p> Signup and view all the answers

    What should enterprises evaluate to avoid wasted software development effort?

    <p>System requirements and bottlenecks</p> Signup and view all the answers

    What is the result of a well-designed technical architecture in large scale software systems?

    <p>A smooth implementation journey</p> Signup and view all the answers

    Which of the following best describes a key consideration in system design?

    <p>Contemplating futuristic changes</p> Signup and view all the answers

    What primary focus should enterprises have while designing large scale software systems?

    <p>Thoroughly understanding user requirements</p> Signup and view all the answers

    What is a potential consequence of neglecting design considerations in large scale system software?

    <p>Unpredictable user experiences</p> Signup and view all the answers

    What role does understanding business requirements play in system design?

    <p>It informs the technical architecture and user needs</p> Signup and view all the answers

    What is the main focus when balancing the trade-offs in system design?

    <p>Creating a system optimized for user needs</p> Signup and view all the answers

    Which factor is NOT mentioned as a consideration in system design trade-offs?

    <p>Interoperability</p> Signup and view all the answers

    How does bandwidth fundamentally differ from throughput?

    <p>Bandwidth pertains to maximum capacity; throughput is actual data processed.</p> Signup and view all the answers

    What is a common consequence of insufficient bandwidth?

    <p>Network congestion</p> Signup and view all the answers

    In the context of latency and throughput, what happens as latency increases?

    <p>Throughput decreases as latency increases</p> Signup and view all the answers

    Which metric is recommended to capture latency in a system under load?

    <p>Percentiles such as p90</p> Signup and view all the answers

    What is the trade-off described by the CAP theorem?

    <p>Consistency vs Availability</p> Signup and view all the answers

    When considering performance vs scalability, what indicates a performance issue?

    <p>Sluggish response times for a single user</p> Signup and view all the answers

    What is the relationship between latency and throughput?

    <p>Inverse relationship</p> Signup and view all the answers

    Which trade-off is a key consideration when designing a system with scalability in mind?

    <p>Performance vs Load capacity</p> Signup and view all the answers

    Which of the following is a characteristic of a system that prioritizes maintainability?

    <p>Easily understandable code</p> Signup and view all the answers

    In terms of system design trade-offs, what might sacrificing robustness typically lead to?

    <p>Lower costs but increased errors</p> Signup and view all the answers

    What can using look-up tables in an algorithm help achieve in system design?

    <p>Faster request serving through pre-calculated values</p> Signup and view all the answers

    What is a potential downside of focusing too heavily on cost in system design?

    <p>Compromised performance and robustness</p> Signup and view all the answers

    What does the KISS guideline emphasize in system design?

    <p>Creating simple and efficient systems</p> Signup and view all the answers

    Which of the following best defines metrics in the context of system performance?

    <p>Quantitative measures to assess system performance</p> Signup and view all the answers

    What is the significance of observability in large-scale systems?

    <p>It enables real-time monitoring and diagnosis of issues.</p> Signup and view all the answers

    What does TINSTAAFL advocate regarding system design decisions?

    <p>Each decision comes with trade-offs.</p> Signup and view all the answers

    What does the CAP theorem state regarding distributed systems?

    <p>A distributed system can provide at most two of the three guarantees at any time.</p> Signup and view all the answers

    Which statement most accurately describes a fundamental aspect of system design?

    <p>System design must balance competing factors and trade-offs.</p> Signup and view all the answers

    According to the PACELC theorem, what must be chosen in the absence of network partitions?

    <p>Latency or Consistency</p> Signup and view all the answers

    In system design, what role do performance metrics play?

    <p>They help identify trends and detect anomalies.</p> Signup and view all the answers

    Which aspect does observing and measuring metrics not help with in system design?

    <p>Identifying user preferences directly</p> Signup and view all the answers

    What trade-off does the CAP theorem highlight during network failures?

    <p>Consistency must be chosen over availability.</p> Signup and view all the answers

    Why is building a system modularly beneficial?

    <p>It allows for independent testing and validation of modules.</p> Signup and view all the answers

    What does the concept of 'it always depends' suggest in system design?

    <p>Multiple factors influence design choices.</p> Signup and view all the answers

    What is emphasized in the guideline of simplicity in system design?

    <p>Avoiding unnecessary complexity and over-engineering.</p> Signup and view all the answers

    Why is it important to weigh trade-offs in system design?

    <p>To develop systems that meet specific project requirements.</p> Signup and view all the answers

    Which aspect is not specifically mentioned as a characteristic of modular systems?

    <p>Performance</p> Signup and view all the answers

    What can be a consequence of failing to think about trade-offs in system design?

    <p>Poor performance or reliability issues in the final system.</p> Signup and view all the answers

    What happens if a system pursues strong consistency through synchronous communication?

    <p>It adds to high latency.</p> Signup and view all the answers

    What is the primary focus when measuring system performance?

    <p>Quantitative evaluation of key performance indicators.</p> Signup and view all the answers

    How can observability affect system reliability?

    <p>By allowing real-time detection of potential issues.</p> Signup and view all the answers

    What principle is highlighted in the guideline of isolation?

    <p>Create independent components to reduce complexity.</p> Signup and view all the answers

    What often results from choosing a simpler design solution?

    <p>Lower performance or increased latency.</p> Signup and view all the answers

    What does eventual consistency imply in distributed systems?

    <p>Data will eventually reflect the latest write after some time.</p> Signup and view all the answers

    What is a potential trade-off in achieving high levels of system performance?

    <p>Higher complexity in the design.</p> Signup and view all the answers

    Which statement about the PACELC theorem is accurate?

    <p>It provides a framework for understanding trade-offs in normal operation and during partitioning.</p> Signup and view all the answers

    What guideline advises to ensure easy usability of the system?

    <p>Guideline of Simplicity</p> Signup and view all the answers

    Which factor is crucial when designing modular systems according to the content?

    <p>Controlling data flows and dependencies between modules.</p> Signup and view all the answers

    What characterizes systems that are designed using the PACELC theorem?

    <p>They involve a choice between availability and consistency during partitions and latency and consistency otherwise.</p> Signup and view all the answers

    Which principle ensures that modules can be reused in different projects?

    <p>Modularity</p> Signup and view all the answers

    What is the primary characteristic of synchronous communication in system design?

    <p>It blocks the sender until a response is received.</p> Signup and view all the answers

    Which of the following best describes the difference between synchronous and asynchronous communication?

    <p>Synchronous waits for a reply while asynchronous does not.</p> Signup and view all the answers

    In the context of data storage, what does consistency ensure?

    <p>Data updates are reflected immediately across all nodes.</p> Signup and view all the answers

    What is an example of asynchronous communication?

    <p>Sending a text message and waiting for a reply.</p> Signup and view all the answers

    Which concept refers to the ability of a system to continue operating in the event of a failure?

    <p>Fault tolerance</p> Signup and view all the answers

    When is synchronous communication most appropriately used in a software system?

    <p>When immediate feedback is necessary.</p> Signup and view all the answers

    What is meant by 'abstraction' in system design?

    <p>The process of eliminating complexity in systems.</p> Signup and view all the answers

    What does scalability refer to in system design?

    <p>The potential to add resources to meet increasing demands.</p> Signup and view all the answers

    In distributed systems, what does a consistency issue often refer to?

    <p>Replica nodes not having the same view of data.</p> Signup and view all the answers

    Why is asynchronous communication considered flexible?

    <p>It does not require simultaneous user presence.</p> Signup and view all the answers

    What is a common challenge associated with consistency in large-scale systems?

    <p>Maintaining uniformity across geographically dispersed nodes.</p> Signup and view all the answers

    What role does 'fault tolerance' play in system design?

    <p>It allows systems to recover from or continue despite failures.</p> Signup and view all the answers

    What aspect of system design is concerned with how effectively a system can remain available?

    <p>Reliability</p> Signup and view all the answers

    Why might a system designer choose asynchronous communication over synchronous?

    <p>To allow processes to proceed without waiting for feedback.</p> Signup and view all the answers

    What technique is primarily used to log writes before applying them to data?

    <p>Write-ahead logging</p> Signup and view all the answers

    Which of the following models ensures that once a client reads a value, all subsequent reads return the same or a more recent value?

    <p>Monotonic read consistency</p> Signup and view all the answers

    What is used to resolve conflicts when multiple replica nodes attempt to update the same data simultaneously?

    <p>Conflict resolution algorithms</p> Signup and view all the answers

    Which consistency level guarantees that all replica nodes reflect the same data at all times?

    <p>Strong consistency</p> Signup and view all the answers

    What does locking in data storage systems primarily ensure?

    <p>Only one write operation can occur at a time</p> Signup and view all the answers

    What is the primary purpose of consensus protocols in distributed systems?

    <p>To ensure all replica nodes agree on updates</p> Signup and view all the answers

    What technique allows concurrent writes while ensuring reads return the most recent write?

    <p>Data versioning</p> Signup and view all the answers

    What does causal consistency guarantee in the context of operations?

    <p>Dependent operations are preserved in order</p> Signup and view all the answers

    Which statement best describes 'eventual consistency'?

    <p>Data may be temporarily inconsistent but will converge to a consistent state eventually</p> Signup and view all the answers

    What is the primary challenge when implementing strong consistency in distributed systems?

    <p>Constant communication among all replica nodes</p> Signup and view all the answers

    What does monotonic write consistency ensure about write operations?

    <p>Once acknowledged, all subsequent reads reflect the updated value</p> Signup and view all the answers

    Which technique is fundamental for restoring data consistency after a system crash?

    <p>Write-ahead logging</p> Signup and view all the answers

    What does the consistency spectrum model help reason about in distributed systems?

    <p>The various consistency guarantees offered by the system</p> Signup and view all the answers

    Which of the following describes the active-passive failover pattern?

    <p>One primary system actively processes requests while backup systems are passive.</p> Signup and view all the answers

    What is a potential issue with multi leader replication?

    <p>Increased risk of data consistency due to conflicting writes.</p> Signup and view all the answers

    Which technique is primarily used to improve system availability?

    <p>Load balancing</p> Signup and view all the answers

    In the context of failover systems, what is the primary advantage of the active-active pattern?

    <p>Higher flexibility and better resource utilization.</p> Signup and view all the answers

    What can be a consequence of using single leader replication?

    <p>Possibility of reduced availability if the leader fails.</p> Signup and view all the answers

    Which of the following is NOT a technique to enhance system availability?

    <p>Error-prone coding</p> Signup and view all the answers

    What is a key trade-off of an active-active failover system?

    <p>Higher costs due to redundancy in resources.</p> Signup and view all the answers

    How does replication contribute to system availability?

    <p>By maintaining multiple copies of data to prevent failure.</p> Signup and view all the answers

    What is a characteristic of the active-active failover strategy?

    <p>Complex management is required due to simultaneous activity.</p> Signup and view all the answers

    What role does load balancing play in system design?

    <p>Distributing workload across multiple resources to enhance efficiency.</p> Signup and view all the answers

    Which of the following can lead to data loss in failover systems?

    <p>Failing to properly manage backup activation timings.</p> Signup and view all the answers

    What is the primary objective of using redundancy in a system?

    <p>To maintain functionality despite component failures.</p> Signup and view all the answers

    Which type of replication pattern allows writing to multiple systems at the same time?

    <p>Multi leader replication</p> Signup and view all the answers

    What effect does the use of multiple read replicas have on replication lag?

    <p>It increases replication lag due to more writes needing replication.</p> Signup and view all the answers

    Which of the following best defines reliability in system design?

    <p>The system's ability to perform functions consistently over time.</p> Signup and view all the answers

    What does the term Mean Time Between Failures (MTBF) measure?

    <p>The average time a system operates without experiencing a failure.</p> Signup and view all the answers

    How is Mean Time to Repair (MTTR) characterized?

    <p>It is the average time required to repair a system after a failure.</p> Signup and view all the answers

    Which is true about the relationship between reliability and availability?

    <p>A system can be reliable but not available at the same time.</p> Signup and view all the answers

    What is vertical scaling in the context of system design?

    <p>Upgrading a single server with better resources to handle load.</p> Signup and view all the answers

    What advantage does horizontal scaling offer over vertical scaling?

    <p>It is less costly than upgrading a single high-end server.</p> Signup and view all the answers

    In which scenario is vertical scaling particularly useful?

    <p>When traffic is predictable and can be handled by a stronger server.</p> Signup and view all the answers

    What challenge arises with the use of multiple read replicas?

    <p>It complicates the process of write replication.</p> Signup and view all the answers

    What does scalability in system design ensure?

    <p>The system's performance improves as more resources are added.</p> Signup and view all the answers

    Which of the following statements is true regarding the implementation of redundancy?

    <p>Redundancy is vital for achieving high reliability and availability.</p> Signup and view all the answers

    What is the overall goal of using MTBF and MTTR measurements in a system?

    <p>To measure and enhance the reliability of the system.</p> Signup and view all the answers

    Which challenge is associated with vertical scaling?

    <p>Limits on how much a single server can scale up.</p> Signup and view all the answers

    What does eventual consistency guarantee in a distributed system?

    <p>Data may be temporarily inconsistent before reconciliation.</p> Signup and view all the answers

    Which metric is used to quantify the availability of a system?

    <p>Total system uptime as a percentage of total operational time.</p> Signup and view all the answers

    What is the primary trade-off involved in the consistency spectrum model?

    <p>Consistency vs. availability in system design.</p> Signup and view all the answers

    Which of the following scenarios describes a system with high availability?

    <p>The system shows some downtime but remains functional under stress.</p> Signup and view all the answers

    How does the arrangement of components in a system affect overall availability?

    <p>Components in parallel can lead to higher total availability than identical components in sequence.</p> Signup and view all the answers

    What is a key challenge in achieving 'five nines' availability?

    <p>Higher levels of redundancy and rigorous maintenance are needed.</p> Signup and view all the answers

    If two components both have an availability of 99.9% and are arranged in sequence, what will be the overall availability?

    <p>99.8%</p> Signup and view all the answers

    Which factor does NOT affect the realism of achieving high levels of availability?

    <p>Consumer demand for quicker transactions.</p> Signup and view all the answers

    What does the term 'availability percentages represented in 9s' indicate?

    <p>The duration of downtime over a specified period.</p> Signup and view all the answers

    What is commonly involved in maintaining high availability in a system?

    <p>Redundant components and continuous monitoring.</p> Signup and view all the answers

    What does a higher level of availability often require regarding system architecture?

    <p>More complex architectures with extensive redundancies.</p> Signup and view all the answers

    What is the implication of assuming that the network is reliable in distributed system design?

    <p>It leads to potential failures due to unforeseen network outages.</p> Signup and view all the answers

    Why is the assumption that latency is zero problematic in distributed systems?

    <p>It ignores the physical limitations of data transmission.</p> Signup and view all the answers

    What happens to the overall availability in a sequential system if one component fails?

    <p>Overall availability drops to zero.</p> Signup and view all the answers

    Which of the following describes the primary difference between strong consistency and eventual consistency?

    <p>Strong consistency guarantees immediate data replication while eventual consistency does not.</p> Signup and view all the answers

    What consequence might arise from assuming infinite bandwidth in network design?

    <p>It can lead to unmanageable data flow and subsequent packet loss.</p> Signup and view all the answers

    Which fallacy relates to the misconception that network security is guaranteed?

    <p>Secure Network</p> Signup and view all the answers

    What is a consequence of arranging components in a sequential system?

    <p>Increased latency due to waiting on responses.</p> Signup and view all the answers

    How does the assumption of a fixed topology complicate distributed system design?

    <p>It fails to account for changes in node availability.</p> Signup and view all the answers

    What is a primary concern when inferring a single administrator for distributed systems?

    <p>It underestimates the complexity of system management.</p> Signup and view all the answers

    What does the assumption of zero transport cost overlook in network design?

    <p>The cumulative expenses involved in network infrastructure maintenance.</p> Signup and view all the answers

    Why is it important to account for a heterogeneous network when designing distributed systems?

    <p>It enables interoperability among differing systems and protocols.</p> Signup and view all the answers

    What might be a direct result of neglecting the fallacies in distributed systems during implementation?

    <p>Higher likelihood of system failures and performance bottlenecks.</p> Signup and view all the answers

    Which AWS Well-Architected Framework pillar addresses the fallacy of assuming a secure network?

    <p>Security</p> Signup and view all the answers

    How can the assumption of network reliability impact system administration complexity?

    <p>It can lead to oversights in necessary maintenance routines.</p> Signup and view all the answers

    What approach can help mitigate the risks associated with assuming zero latency in distributed systems?

    <p>Implementing edge computing solutions.</p> Signup and view all the answers

    What is a potential effect of neglecting the fallacy of infinite bandwidth in distributed network designs?

    <p>Increased likelihood of network congestion and data losses.</p> Signup and view all the answers

    What is a primary benefit of horizontal scaling for managing unpredictable traffic?

    <p>It increases server capacity to handle more requests.</p> Signup and view all the answers

    What aspect of maintainability involves a system being easy to modify or extend?

    <p>Modifiability</p> Signup and view all the answers

    Which mechanism ensures that a system can recover from a failure and continue to serve requests?

    <p>Replication</p> Signup and view all the answers

    What does synchronous checkpointing require from the system during the checkpointing process?

    <p>Only read requests are allowed.</p> Signup and view all the answers

    Which of the following is NOT a component of maintainability in system design?

    <p>Inflexibility</p> Signup and view all the answers

    What is a primary risk associated with asynchronous checkpointing?

    <p>It can create inconsistent data states across servers.</p> Signup and view all the answers

    Which aspect of a system does operability emphasize on?

    <p>Smooth operation under normal conditions</p> Signup and view all the answers

    To adapt to changing business needs, software systems must prioritize which of these aspects?

    <p>Modifiability</p> Signup and view all the answers

    How does replication contribute to fault tolerance?

    <p>By duplicating services and data across multiple servers.</p> Signup and view all the answers

    What is the main function of checkpointing in a system?

    <p>To ensure data integrity and reliability.</p> Signup and view all the answers

    In large-scale systems, what does fault tolerance primarily aim to eliminate?

    <p>Single points of failure</p> Signup and view all the answers

    What is the role of lucidity in a software system?

    <p>To enhance understanding and collaboration among team members.</p> Signup and view all the answers

    Which of the following is a vital characteristic of highly maintainable systems?

    <p>Modular design</p> Signup and view all the answers

    What is the purpose of having multiple copies of data in replication?

    <p>To ensure data availability and recovery during failures.</p> Signup and view all the answers

    What is the primary goal when balancing trade-offs in system design?

    <p>To optimize for user needs without sacrificing critical factors</p> Signup and view all the answers

    What does the CAP theorem address in system design?

    <p>The balance between consistency and high availability</p> Signup and view all the answers

    Which trade-off involves managing the speed of requests versus the ability to handle increased demand?

    <p>Performance vs Scalability</p> Signup and view all the answers

    Which metric is more empirical and measures actual data transmission in a network?

    <p>Throughput</p> Signup and view all the answers

    What does it mean if a system is experiencing high latency?

    <p>Requests are delayed and waiting to be handled</p> Signup and view all the answers

    If a system prioritizes cost, which of the following factors may be sacrificed?

    <p>All of the above</p> Signup and view all the answers

    Which of the following best defines latency in a network context?

    <p>The time a request waits to be handled</p> Signup and view all the answers

    What happens to throughput as latency increases?

    <p>Throughput decreases</p> Signup and view all the answers

    A system that is designed for both high reliability and scalability may result in which trade-off?

    <p>Increased need for expensive components</p> Signup and view all the answers

    Why is average latency not used as a metric in system design?

    <p>It can be affected by outliers</p> Signup and view all the answers

    In what situation might you prioritize scalability over performance?

    <p>In an environment anticipating rapid growth in user demand</p> Signup and view all the answers

    Which of these concepts relates to the actual capacity of a network under specific conditions?

    <p>Throughput</p> Signup and view all the answers

    Which of the following accurately captures the relationship between latency and throughput?

    <p>They have an inverse relationship</p> Signup and view all the answers

    What would likely be a consequence of insufficient bandwidth in a network?

    <p>Network congestion and slow connectivity</p> Signup and view all the answers

    Which guarantees can a distributed system provide simultaneously according to the CAP theorem?

    <p>Consistency and Partition Tolerance</p> Signup and view all the answers

    When a network partition occurs, what trade-off must a distributed system make according to the CAP theorem?

    <p>Consistency and Availability</p> Signup and view all the answers

    What does the PACELC theorem specify when there are no network partitions?

    <p>Choose between consistency and latency</p> Signup and view all the answers

    Which guideline focuses on restructuring a system into smaller independent components?

    <p>Guideline of Isolation</p> Signup and view all the answers

    Which approach supports reusability in system design?

    <p>Modular system design</p> Signup and view all the answers

    What is the main consequence of prioritizing complexity over simplicity in system design?

    <p>Difficulty in understanding and use</p> Signup and view all the answers

    What is a characteristic of synchronous communication within a distributed system?

    <p>All parties must be available and responsive</p> Signup and view all the answers

    Which of the following would NOT align with the Keep it Simple, Silly (KISS) principle in system design?

    <p>Adding numerous unnecessary features</p> Signup and view all the answers

    Which is a key advantage of maintaining modularity in a system design?

    <p>Reduced risk of system-wide failures</p> Signup and view all the answers

    Why might a team opt for eventual consistency in a distributed system?

    <p>To enable higher performance with lower latency</p> Signup and view all the answers

    What aspect should be prioritized when designing to accommodate growth in large scale systems?

    <p>Scalability of components</p> Signup and view all the answers

    Which of the following statements best reflects the purpose of the CAP theorem in system design?

    <p>Describes trade-offs among consistency, availability, and partition tolerance</p> Signup and view all the answers

    What could be a negative outcome of excessive modularity in system design?

    <p>Increased difficulty in managing module interfaces</p> Signup and view all the answers

    What does the KISS guideline emphasize in system design?

    <p>Creating simple, efficient, and maintainable systems</p> Signup and view all the answers

    Which of the following best describes observability in system design?

    <p>Inferring the state of a system from its outputs</p> Signup and view all the answers

    What does TINSTAAFL imply in system design?

    <p>Optimizing for one aspect may compromise another</p> Signup and view all the answers

    Which of the following is NOT a factor considered in system design?

    <p>Personal preferences of the developer</p> Signup and view all the answers

    How do metrics contribute to system performance management?

    <p>By tracking key performance indicators</p> Signup and view all the answers

    Why is it necessary to measure before building systems?

    <p>To gather data that informs decisions and optimizations</p> Signup and view all the answers

    In system design, what is the significance of balancing competing factors?

    <p>It helps in producing systems that meet specific requirements</p> Signup and view all the answers

    What happens when simplicity is prioritized excessively in system design?

    <p>Reduction in maintainability and increase in complexity</p> Signup and view all the answers

    What role does observability play in managing large-scale systems?

    <p>To allow detection of real-time issues impacting performance</p> Signup and view all the answers

    Which statement illustrates the importance of trade-offs in system design?

    <p>Optimizing one aspect often detracts from others.</p> Signup and view all the answers

    What is implied by the statement, 'It always depends' in system design?

    <p>All design choices are context-dependent.</p> Signup and view all the answers

    How can metrics and observability work together in system design?

    <p>Metrics provide quantitative data, while observability aids in diagnostics.</p> Signup and view all the answers

    What should system designers recognize about solutions in the context of trade-offs?

    <p>Solutions must consider potential trade-offs and implications.</p> Signup and view all the answers

    What can be a likely consequence of neglecting performance metrics?

    <p>Failure to identify performance bottlenecks</p> Signup and view all the answers

    Study Notes

    System Design Overview

    • Large-scale software systems are fundamental to modern technological advancements, evidenced by companies like Google, Amazon, Oracle, and SAP.
    • First principles thinking is critical in designing technical architecture to prevent issues later in the implementation process.

    Importance of System Design

    • Successful system design focuses on business requirements, customer needs, and various trade-offs to ensure long-term functionality.
    • Careful consideration of system bottlenecks and user access patterns is essential for effective system design.

    Foundational Concepts in System Design

    • Key concepts include:
      • Communication
      • Consistency
      • Availability
      • Reliability
      • Scalability
      • Fault tolerance
      • System maintainability

    Communication Mechanisms

    • Synchronous Communication:

      • Example: Real-time phone conversations where both parties communicate simultaneously.
      • The application waits for responses before proceeding, potentially causing perceived latency.

    • Asynchronous Communication:

      • Example: Email exchanges allowing delayed responses.
      • The sender does not wait for replies, facilitating flexibility and resilience in applications.

    Consistency in Systems

    • Consistency ensures all parts of a distributed system view data uniformly, pertinent in contexts like data storage and retrieval.
    • Consistency Techniques in distributed systems:
      • Data Replication: Multiple replicas are updated simultaneously for uniformity.
      • Consensus Protocols: Ensure agreement on data updates among nodes.
      • Conflict Resolution: Mechanisms to handle simultaneous conflicting updates from different replicas.

    Consistency in Data Storage

    • Techniques to maintain consistency in data storage include:
      • Write-ahead Logging: Logs write operations before application to data.
      • Locking Mechanisms: Control concurrent write access.
      • Data Versioning: Allows multiple concurrent writes while preserving read consistency.

    Consistency Spectrum Model

    • Consistency ranges from Eventual Consistency (leading to flexibility with potential data stale states) to Strong Consistency (ensuring all replicas are updated immediately after a write).

    Availability in Systems

    • Availability measures a system's capacity to serve requests effectively, even under failures.
    • Calculated as the proportion of uptime to total operational time, expressed as a percentage of the “nines” (e.g., 99.9999% represents six nines).

    Achieving High Availability

    • Each increment in availability comes with increased cost and complexity.
    • Techniques include:
      • Redundancy: Having backup components to maintain function amid failures.
      • Fault Tolerance: System resilience against unpredictable errors.

    System Arrangement Impacting Availability

    • Sequential Systems: The overall availability is multiplied across components; e.g., two 99.9% components yield 99.8% availability.
    • Parallel Systems: Availability is significantly improved as components can serve requests simultaneously, leading to a maintained uptime (e.g., two 99.9% components yield 99.9999% availability).

    Ensuring System Availability

    • Critical for maintaining performance and reliability through methods like redundancy and fault tolerance to navigate failure scenarios effectively.### Availability Mechanisms
    • Systems can achieve high availability through error-handling mechanisms, redundant hardware, or self-healing systems.
    • Load balancing distributes incoming requests across multiple servers to efficiently manage heavy loads and enhance availability.
    • Active-active and active-passive are the two primary failover patterns utilized to maintain system availability.

    Failover Patterns

    • Active-active failover: Multiple systems process requests in parallel; if one fails, others continue operations, providing flexibility but increasing complexity.
    • Active-passive failover: One primary system handles requests while passive backups wait to take over if the primary fails. This method is simpler but can cause delays during failover, reducing availability.

    Replication Patterns

    • Replication maintains multiple data copies to enhance availability and fault tolerance, with multi-leader and single-leader formats being the two main types.
    • Multi-leader replication: Multiple systems can read and write data, offering flexibility but increasing complexity and potential latency due to conflict resolution.
    • Single-leader replication: A single leader manages commands while followers replicate data for read operations only. This approach risks data loss if the leader fails and can lead to replication lag.

    Reliability Measurement

    • Reliability reflects a system's consistency in performing intended functions. Key metrics include:
      • Mean Time Between Failures (MTBF): Time a system operates without failure; higher is more reliable.
      • Mean Time to Repair (MTTR): Time to restore a system after failure; lower is better.

    Reliability vs. Availability

    • Reliability and availability are interrelated; a reliable but unavailable system fails at critical times, while an available but unreliable system may perform erratically.
    • Meeting service level objectives (SLOs) requires incorporating redundancy and failover mechanisms alongside regular maintenance.

    Scalability

    • Scalability ensures system performance improves with additional resources in response to increased workloads, whether from user requests or data storage needs.
    • Vertical scaling enhances a single server's capabilities but has limits and high costs associated with resource upgrades.
    • Horizontal scaling involves adding multiple servers, providing cost-effective scalability for variable traffic levels but adds management complexity.

    Maintainability

    • Maintainability allows a system to adapt to changing user needs without disrupting operations. Three key aspects include:
      • Operability: The system should function smoothly and resume operations quickly after faults.
      • Lucidity: A clear and understandable system promotes efficient collaboration and easier maintenance.
      • Modifiability: Modular systems enable smooth changes without impacting other components.

    Fault Tolerance

    • Fault tolerance enables continuous operation despite failures through effective request rerouting and redundancy.
    • Replication: Clones services and data across multiple servers for safety and inherent data accessibility.
    • Checkpointing: Backups the system's state to restore it following data loss or corruption, employing synchronous or asynchronous methods for checkpoint creation.

    Fallacies of Distributed Computing

    • Reliable Network: Networks are often unstable; design for potential faults.
    • Zero Latency: Latency is unavoidable; optimize proximity to data through edge-computing and strategic server placement.
    • Infinite Bandwidth: Network resource contention leads to limits; use lightweight data formats and multiplexing to optimize bandwidth.
    • Secure Network: A network is not inherently secure; adopt a security-first approach and conduct thorough assessments.
    • Fixed Topology: Network topologies fluctuate continuously due to system changes; design must account for dynamism.### System Design Fallacies
    • Fixed topology assumptions can lead to issues such as latency and bandwidth problems; systems should be designed to be topology-agnostic.
    • The assumption of a "Single Administrator" fails in large-scale distributed systems due to multiple teams and OS; systems need decoupled designs for easier troubleshooting.
    • "Zero Transport Cost" is a fallacy; network infrastructure requires investment in hardwares, software, and teams, thus costs must be accounted in budgets.
    • Networks are not homogeneous; variations in device configurations and protocols necessitate an emphasis on interoperability among subsystems.

    AWS Well-Architected Framework

    • The framework consists of six core pillars designed to guide system design and mitigate common fallacies.
    • Pillars include:
      • Operational Excellence: Avoids issues related to Single Administrator and Homogeneous Network.
      • Security: Addresses the Secure Network fallacy.
      • Reliability: Counters Reliable Network and Fixed Topology fallacies.
      • Performance Efficiency: Tackles Zero Latency and Infinite Bandwidth assumptions.
      • Cost Optimization & Sustainability: Overcome the Zero Transport Cost assumption.

    System Design Trade-offs

    • Balancing cost, scalability, reliability, maintainability, and robustness is crucial when designing large-scale systems.
    • Performance trade-offs may require decisions between higher reliability with greater costs versus budget constraints impacting robustness and scalability.

    Time vs Space Trade-off

    • Time-memory trade-offs are essential; choosing between quick calculations using more memory or time-consuming recalculations must be respected in algorithm design.

    Latency vs Throughput

    • Latency is the time a request waits, while throughput measures actual data processed; these metrics have an inverse relationship, as increased latency reduces throughput.
    • Percentile metrics (e.g., p90 latency) gauge performance more effectively than average latency.

    Performance vs Scalability

    • Performance focuses on single request efficiency; scalability deals with system behavior under increased load; both aspects require careful management to meet user demands.

    Consistency vs Availability (CAP Theorem)

    • CAP Theorem states it's impossible to guarantee consistency, availability, and partition tolerance simultaneously in a distributed system.
    • Systems must prioritize either consistency or availability during network failures, emphasizing partition tolerance in designs.

    PACELC Theorem

    • PACELC expands on CAP, indicating the need to balance between availability and consistency during partitions and between latency and consistency otherwise.

    System Design Guidelines

    • Isolation: Develop modular systems for ease of maintenance, reusability, scalability, and reliability.
    • Simplicity: Employ KISS principles to build straightforward systems that focus on core requirements without unnecessary complexity.
    • Performance: Utilize metrics and observability as critical components to assess system performance and preempt issues.
    • Trade-offs: Recognize that optimizing one factor often affects others; value careful consideration in system design choices.
    • Use Cases: Understand that each design decision depends on specific user needs, constraints, and contextual factors, emphasizing custom solutions over one-size-fits-all approaches.

    Conclusion

    • Effective system design requires balancing competing factors and understanding the broader implications of decisions.
    • Future chapters will delve into foundational concepts related to data storage, caching, load balancing, and networking within system architecture.

    System Design Overview

    • Large-scale software systems are fundamental to modern technological advancements, evidenced by companies like Google, Amazon, Oracle, and SAP.
    • First principles thinking is critical in designing technical architecture to prevent issues later in the implementation process.

    Importance of System Design

    • Successful system design focuses on business requirements, customer needs, and various trade-offs to ensure long-term functionality.
    • Careful consideration of system bottlenecks and user access patterns is essential for effective system design.

    Foundational Concepts in System Design

    • Key concepts include:
      • Communication
      • Consistency
      • Availability
      • Reliability
      • Scalability
      • Fault tolerance
      • System maintainability

    Communication Mechanisms

    • Synchronous Communication:

      • Example: Real-time phone conversations where both parties communicate simultaneously.
      • The application waits for responses before proceeding, potentially causing perceived latency.

    • Asynchronous Communication:

      • Example: Email exchanges allowing delayed responses.
      • The sender does not wait for replies, facilitating flexibility and resilience in applications.

    Consistency in Systems

    • Consistency ensures all parts of a distributed system view data uniformly, pertinent in contexts like data storage and retrieval.
    • Consistency Techniques in distributed systems:
      • Data Replication: Multiple replicas are updated simultaneously for uniformity.
      • Consensus Protocols: Ensure agreement on data updates among nodes.
      • Conflict Resolution: Mechanisms to handle simultaneous conflicting updates from different replicas.

    Consistency in Data Storage

    • Techniques to maintain consistency in data storage include:
      • Write-ahead Logging: Logs write operations before application to data.
      • Locking Mechanisms: Control concurrent write access.
      • Data Versioning: Allows multiple concurrent writes while preserving read consistency.

    Consistency Spectrum Model

    • Consistency ranges from Eventual Consistency (leading to flexibility with potential data stale states) to Strong Consistency (ensuring all replicas are updated immediately after a write).

    Availability in Systems

    • Availability measures a system's capacity to serve requests effectively, even under failures.
    • Calculated as the proportion of uptime to total operational time, expressed as a percentage of the “nines” (e.g., 99.9999% represents six nines).

    Achieving High Availability

    • Each increment in availability comes with increased cost and complexity.
    • Techniques include:
      • Redundancy: Having backup components to maintain function amid failures.
      • Fault Tolerance: System resilience against unpredictable errors.

    System Arrangement Impacting Availability

    • Sequential Systems: The overall availability is multiplied across components; e.g., two 99.9% components yield 99.8% availability.
    • Parallel Systems: Availability is significantly improved as components can serve requests simultaneously, leading to a maintained uptime (e.g., two 99.9% components yield 99.9999% availability).

    Ensuring System Availability

    • Critical for maintaining performance and reliability through methods like redundancy and fault tolerance to navigate failure scenarios effectively.### Availability Mechanisms
    • Systems can achieve high availability through error-handling mechanisms, redundant hardware, or self-healing systems.
    • Load balancing distributes incoming requests across multiple servers to efficiently manage heavy loads and enhance availability.
    • Active-active and active-passive are the two primary failover patterns utilized to maintain system availability.

    Failover Patterns

    • Active-active failover: Multiple systems process requests in parallel; if one fails, others continue operations, providing flexibility but increasing complexity.
    • Active-passive failover: One primary system handles requests while passive backups wait to take over if the primary fails. This method is simpler but can cause delays during failover, reducing availability.

    Replication Patterns

    • Replication maintains multiple data copies to enhance availability and fault tolerance, with multi-leader and single-leader formats being the two main types.
    • Multi-leader replication: Multiple systems can read and write data, offering flexibility but increasing complexity and potential latency due to conflict resolution.
    • Single-leader replication: A single leader manages commands while followers replicate data for read operations only. This approach risks data loss if the leader fails and can lead to replication lag.

    Reliability Measurement

    • Reliability reflects a system's consistency in performing intended functions. Key metrics include:
      • Mean Time Between Failures (MTBF): Time a system operates without failure; higher is more reliable.
      • Mean Time to Repair (MTTR): Time to restore a system after failure; lower is better.

    Reliability vs. Availability

    • Reliability and availability are interrelated; a reliable but unavailable system fails at critical times, while an available but unreliable system may perform erratically.
    • Meeting service level objectives (SLOs) requires incorporating redundancy and failover mechanisms alongside regular maintenance.

    Scalability

    • Scalability ensures system performance improves with additional resources in response to increased workloads, whether from user requests or data storage needs.
    • Vertical scaling enhances a single server's capabilities but has limits and high costs associated with resource upgrades.
    • Horizontal scaling involves adding multiple servers, providing cost-effective scalability for variable traffic levels but adds management complexity.

    Maintainability

    • Maintainability allows a system to adapt to changing user needs without disrupting operations. Three key aspects include:
      • Operability: The system should function smoothly and resume operations quickly after faults.
      • Lucidity: A clear and understandable system promotes efficient collaboration and easier maintenance.
      • Modifiability: Modular systems enable smooth changes without impacting other components.

    Fault Tolerance

    • Fault tolerance enables continuous operation despite failures through effective request rerouting and redundancy.
    • Replication: Clones services and data across multiple servers for safety and inherent data accessibility.
    • Checkpointing: Backups the system's state to restore it following data loss or corruption, employing synchronous or asynchronous methods for checkpoint creation.

    Fallacies of Distributed Computing

    • Reliable Network: Networks are often unstable; design for potential faults.
    • Zero Latency: Latency is unavoidable; optimize proximity to data through edge-computing and strategic server placement.
    • Infinite Bandwidth: Network resource contention leads to limits; use lightweight data formats and multiplexing to optimize bandwidth.
    • Secure Network: A network is not inherently secure; adopt a security-first approach and conduct thorough assessments.
    • Fixed Topology: Network topologies fluctuate continuously due to system changes; design must account for dynamism.### Fallacies in System Design
    • Fixed topology assumptions lead to system issues due to latency and bandwidth constraints; systems must be agnostic to underlying topology.
    • The “Single Administrator” fallacy fails in large distributed systems; design should be decoupled for easier repair and troubleshooting given multiple teams and OSs.
    • The notion of “Zero Transport Cost” overlooks network infrastructure expenses, necessitating budget considerations for servers, switches, and maintenance teams.
    • Networks are heterogeneous, contrary to the “Homogeneous Network” fallacy; interoperability is essential for systems to function across diverse devices and protocols.

    AWS Well-Architected Framework

    • Comprises six core pillars for designing robust AWS systems:
      • Operational Excellence: Addresses the fallacies of Single Administrator and Homogeneous Network.
      • Security: Tackles the assumption of a Secure Network.
      • Reliability: Mitigates Fixed Topology and Reliable Network assumptions.
      • Performance Efficiency: Resolves issues related to Zero Latency and Infinite Bandwidth.
      • Cost Optimization and Sustainability: Counteracts Zero Transport Cost misconceptions.

    System Design Trade-offs

    • System design necessitates balancing cost, scalability, reliability, maintainability, and robustness to meet user needs.
    • Performance and scalability must be weighed; reliable systems may require expensive components for future scalability.
    • The Time vs Space trade-off arises when algorithmic performance is optimized using additional memory or storage.
    • Latency vs Throughput: As system load increases, latency metrics decline when aiming for higher throughput. Throughput measures actual data transmission, whereas bandwidth indicates potential limits.
    • Performance vs Scalability: A scalable system improves performance proportionally with additional resources, but may encounter latency under heavy user demand.
    • Consistency vs Availability: The CAP theorem states a distributed system cannot ensure consistency, availability, and partition tolerance simultaneously; typically, two of these are prioritized when faced with network partitions.

    CAP and PACELC Theorems

    • CAP Theorem: In distributed systems, one must choose between consistency and availability during network partitions.
    • PACELC Theorem: Extends CAP by indicating that in absence of network partition, trade-offs exist between latency and consistency.

    System Design Guidelines

    • Isolation: Modular systems enhance maintainability, reusability, scalability, and reliability by breaking down complexity into independent components.
    • Simplicity: KISS principle focuses on minimizing complexities and unnecessary features. Prioritize core requirements and avoid over-engineering.
    • Performance Metrics: Metrics and observability are critical; they provide baseline measurements for assessing system performance and identifying issues.
    • Trade-offs: Recognize that all design decisions involve trade-offs; optimizing one aspect often compromises another.
    • Use Cases: Emphasize that design depends on specific factors, and there is no universal approach in system design solutions.

    Conclusion

    • Effective system design requires balancing various trade-offs, understanding fallacies, and following established guidelines.
    • Next chapters will delve into fundamental aspects of systems, such as data storage, caching, load balancing, and communication networks.

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