Software Development Fundamentals

System Design Concepts

• Stateless services are easier to scale and manage.

Deployment Pipeline

• A deployment pipeline automates the process of building, testing, and deploying software.
• Typical stages include source code management, build, automated tests, deployment to staging, and deployment to production.

Database Normalization

• Database normalization is the process of organizing data in a relational database to reduce redundancy and improve data integrity.
• It involves dividing tables into smaller, related tables and defining relationships between them.

Virtual Machines and Containers

• A virtual machine (VM) emulates a complete computer system, including the hardware, allowing multiple OS instances on a single physical machine.
• Containers, however, share the host OS kernel and are more lightweight and efficient.

Quorum in Distributed Systems

• A quorum is the minimum number of votes that must be gathered from a group of nodes to perform an operation in a distributed system.
• It ensures that a majority agreement is reached, helping in maintaining consistency and fault tolerance.

Consistency Models

• Strong consistency ensures that any read operation will return the most recent write for a given piece of data.
• Eventual consistency allows reads to return older versions of the data but guarantees that, eventually, all updates will be propagated to all nodes.

Single Point of Failure

• A single point of failure (SPOF) is a component in a system that, if it fails, will stop the entire system from functioning.
• It can be mitigated by introducing redundancy and load balancing.

Distributed Systems

• A distributed system is a network of independent computers that appear to the user as a single coherent system.
• Key characteristics include scalability, fault tolerance, concurrency, and transparency.

Load Balancing

• A load balancer distributes incoming network traffic across multiple servers to ensure no single server becomes a bottleneck.
• It helps improve responsiveness and availability.

Scaling

• Horizontal scaling involves adding more machines to a system to handle increased load.
• Vertical scaling involves adding more resources (CPU, RAM) to an existing machine.

Microservices

• A microservice is a small, independent service that performs a specific function.
• It differs from a monolithic application, which is a single, large application with tightly coupled components.

NoSQL Databases

• A NoSQL database is a non-relational database that can store and retrieve data differently than traditional SQL databases.
• It's used when scalability, flexibility, and performance are more important than strict consistency.

CAP Theorem

• CAP theorem states that in any distributed system, only two out of three guarantees (Consistency, Availability, Partition tolerance) can be achieved at the same time.
• It implies trade-offs must be made in system design.

Eventual Consistency

• Eventual consistency ensures that, given enough time, all replicas of data will converge to the same value.
• It's acceptable in scenarios where immediate consistency is not critical.

Message Brokers

• A message broker is an intermediary that facilitates the exchange of information between systems or applications.
• It decouples the producers and consumers of messages, improving scalability and fault tolerance.

API Architectures

• A RESTful API uses HTTP requests to perform CRUD operations on resources.
• SOAP API is a protocol that uses XML to encode messages and relies on other application layer protocols.

Reverse Proxies

• A reverse proxy is a server that sits between client devices and backend servers, forwarding client requests to the appropriate backend server.
• It's used for load balancing, caching, and security purposes.

Content Delivery Networks (CDNs)

• A CDN is a network of servers distributed across different locations to deliver web content more efficiently.
• It improves performance by caching content closer to end-users and reducing latency.

Communication Models

• Synchronous communication requires both parties to be available and engaged at the same time.
• Asynchronous communication allows parties to interact without requiring simultaneous availability, often via message queues or notifications.

Circuit Breaker Pattern

• A circuit breaker pattern prevents an application from repeatedly trying to execute an operation that's likely to fail, by stopping the operation for a defined period.
• It helps in fault tolerance.