AWS ElastiCache
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Questions and Answers

What is the recommended action if the CPUUtilization metric exceeds 90%?

  • Reduce the ConnectionOverhead parameter value
  • Scale your cache cluster down by using a smaller cache node type
  • Scale your cache cluster up by using a larger cache node type (correct)
  • Investigate the application behavior to address the issue

    • What does the SwapUsage metric measure?

  • The efficiency in the allocation of memory of the Redis engine
  • The number of client connections to the cache cluster
  • The number of successful read-only key lookups in the main dictionary
  • The amount of swap space used in bytes (correct)

    • What is the purpose of Redis Auth?

  • To bill partial Node-hours consumed as full hours
  • To authenticate requests to AWS resources
  • To log all Amazon ElastiCache actions
  • To require a token (password) before allowing clients to run commands (correct)

    • What is the unit of pricing for ElastiCache?

    <p>Node-hour consumed for each Node Type</p> Signup and view all the answers

    What is the recommended value for the MemoryFragmentationRatio metric?

    <p>Above 1.0</p> Signup and view all the answers

    What does the CacheHitRate metric indicate?

    <p>The usage efficiency of the Redis instance</p> Signup and view all the answers

    What type of policies can be used with Amazon ElastiCache to provide necessary access?

    <p>Identity-based policies</p> Signup and view all the answers

    What is the purpose of AWS CloudTrail?

    <p>To log all Amazon ElastiCache actions</p> Signup and view all the answers

    What is the Evictions metric used for?

    <p>To scale the cache cluster up or out</p> Signup and view all the answers

    What is not charged in ElastiCache?

    <p>Data transfer between Amazon EC2 and Amazon ElastiCache within the same Availability Zone</p> Signup and view all the answers

    What is a primary feature of ElastiCache Memcached compared to Redis?

    <p>Offers multi-threaded performance.</p> Signup and view all the answers

    Which statement about ElastiCache clusters is accurate?

    <p>Endpoints are used for applications to connect to clusters.</p> Signup and view all the answers

    Which caching strategy is characterized by automatically loading data when it is requested?

    <p>Lazy Loading</p> Signup and view all the answers

    What is the maximum number of shards allowed in Redis when cluster mode is enabled?

    <p>15</p> Signup and view all the answers

    What is a key use case for ElastiCache?

    <p>Offloading reads from a database.</p> Signup and view all the answers

    Which feature is unique to Redis compared to Memcached?

    <p>Supports data persistence.</p> Signup and view all the answers

    What does TTL stand for in the context of caching?

    <p>Time to Live</p> Signup and view all the answers

    Which of the following options indicates a limitation of ElastiCache Memcached?

    <p>Does not support snapshots.</p> Signup and view all the answers

    What is the primary purpose of maintenance windows in ElastiCache?

    <p>To perform software patching.</p> Signup and view all the answers

    In Redish, how are replicas distributed across availability zones?

    <p>Across multiple availability zones in the same region.</p> Signup and view all the answers

    What is the primary purpose of ElastiCache?

    <p>To provide in-memory caching for better latency and throughput.</p> Signup and view all the answers

    Which statement about ElastiCache nodes is correct?

    <p>Failed nodes are automatically replaced by the service.</p> Signup and view all the answers

    Which of the following statements is true about the billing of ElastiCache?

    <p>Billing is determined by node size and hours of usage.</p> Signup and view all the answers

    What is a characteristic of the ElastiCache service concerning data storage?

    <p>The data is stored in-memory and is not persistent traditionally.</p> Signup and view all the answers

    What are subnet groups in the context of ElastiCache?

    <p>Designated subnets for the Amazon ElastiCache Cluster within a VPC.</p> Signup and view all the answers

    Which of the following is NOT a type of instance for ElastiCache?

    <p>Transactional instances.</p> Signup and view all the answers

    How is access to ElastiCache nodes regulated when deployed in a VPC?

    <p>By VPC security groups and subnet groups.</p> Signup and view all the answers

    Which workload type is ElastiCache best suited for?

    <p>Online Analytics Processing (OLAP) transactions.</p> Signup and view all the answers

    Which option correctly describes the nature of nodes in ElastiCache?

    <p>Nodes are fixed-sized, network-attached RAM elements.</p> Signup and view all the answers

    What happens if an existing ElastiCache Cluster is moved outside of a VPC?

    <p>It must be recreated as a new cluster.</p> Signup and view all the answers

    What is the key use case for ElastiCache?

    <p>Offloading reads from a database, storing the results of computations and session state</p> Signup and view all the answers

    What is the primary purpose of maintenance windows in ElastiCache?

    <p>To allow software patching to occur</p> Signup and view all the answers

    What is a key difference between Redis and Memcached engines?

    <p>Memcached supports multi-threading, Redis does not</p> Signup and view all the answers

    What is a characteristic of the ElastiCache service concerning data storage?

    <p>It's an in-memory database</p> Signup and view all the answers

    What is the maximum number of nodes per region for Memcached?

    <p>100 nodes</p> Signup and view all the answers

    What is the primary purpose of Redis shards?

    <p>To provide a primary node and read replicas</p> Signup and view all the answers

    What is a limitation of ElastiCache Memcached?

    <p>It does not support multi-AZ failover or replication</p> Signup and view all the answers

    What is the primary purpose of Redis replication?

    <p>To provide high availability across availability zones</p> Signup and view all the answers

    What is the difference between Lazy Loading and Write-Through caching strategies?

    <p>Lazy Loading loads data when requested, Write-Through loads data in advance</p> Signup and view all the answers

    How is access to ElastiCache nodes regulated when deployed in a VPC?

    <p>Using subnet groups</p> Signup and view all the answers

    What is the primary purpose of ElastiCache?

    <p>To improve application performance by caching data in memory.</p> Signup and view all the answers

    Which type of workloads is ElastiCache best suited for?

    <p>Read-heavy workloads with low latency requirements.</p> Signup and view all the answers

    What is a key characteristic of ElastiCache nodes?

    <p>They are scalable units of secure RAM that can be easily added or removed.</p> Signup and view all the answers

    How is access to ElastiCache nodes regulated when deployed within a VPC?

    <p>Through VPC security groups and subnet groups.</p> Signup and view all the answers

    What are subnet groups in the context of ElastiCache?

    <p>A set of subnets within a VPC that are designated for ElastiCache cluster deployments.</p> Signup and view all the answers

    Which of the following statements is TRUE about ElastiCache billing?

    <p>ElastiCache is billed based on node size and hours of use.</p> Signup and view all the answers

    What is a primary characteristic of ElastiCache's data storage mechanism?

    <p>It is an in-memory key/value store, making it fast but not persistent in the traditional sense.</p> Signup and view all the answers

    Which of the following options is NOT a valid instance type for ElastiCache?

    <p>Cache security groups</p> Signup and view all the answers

    What is a common use case for ElastiCache in terms of application data?

    <p>Caching results of I/O-intensive database queries or computationally intensive calculations.</p> Signup and view all the answers

    Which statement about ElastiCache clusters is accurate?

    <p>They can span multiple subnets of the same subnet group within a VPC.</p> Signup and view all the answers

    Which metric provides insight into the efficiency of memory allocation in ElastiCache Redis?

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

    What is the recommended course of action if the SwapUsage metric for Memcached exceeds 50MB?

    <p>Increase the ConnectionOverhead parameter value.</p> Signup and view all the answers

    Which metric is specifically designed to analyze the load of the Redis process itself?

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

    What is the recommended action if the CacheHitRate metric for Redis falls below ~0.8?

    <p>Investigate the application behavior for potential issues.</p> Signup and view all the answers

    What is the purpose of Redis Auth?

    <p>To require a token before allowing clients to execute Redis commands.</p> Signup and view all the answers

    Which of the following statements is true about ElastiCache pricing?

    <p>The pricing model is based on per-node-hour consumption for each node type.</p> Signup and view all the answers

    What is the primary purpose of AWS CloudTrail in the context of ElastiCache?

    <p>To log all Amazon ElastiCache actions, including who generated the request.</p> Signup and view all the answers

    Which metric indicates the number of successful read-only key lookups in the main Redis dictionary?

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

    Which statement accurately describes the behavior of the Evictions metric for Memcached?

    <p>A high Evictions count might indicate the need to scale the cluster up or out.</p> Signup and view all the answers

    Which of the following options is NOT a characteristic of ElastiCache Memcached?

    <p>It offers advanced features like data persistence and replication.</p> Signup and view all the answers

    What is the primary benefit of using ElastiCache for read-heavy application workloads or compute-intensive workloads?

    <p>To improve latency and throughput</p> Signup and view all the answers

    What is a node in ElastiCache?

    <p>A fixed-sized chunk of secure, network-attached RAM</p> Signup and view all the answers

    What is the purpose of subnet groups in ElastiCache?

    <p>To designating subnets for an Amazon ElastiCache Cluster</p> Signup and view all the answers

    How are failed nodes replaced in ElastiCache?

    <p>Automatically by the system</p> Signup and view all the answers

    What is a key benefit of using ElastiCache with applications that require high performance?

    <p>Offloading reads from a database and storing the results of computations</p> Signup and view all the answers

    What type of workloads is ElastiCache best suited for?

    <p>Read-heavy workloads or compute-intensive workloads</p> Signup and view all the answers

    What is a key difference between the Memcached and Redis engines in ElastiCache?

    <p>Redis supports more complex data structures, while Memcached does not</p> Signup and view all the answers

    What can be stored in ElastiCache?

    <p>Results of I/O-intensive database queries or computationally intensive calculations</p> Signup and view all the answers

    What is the purpose of maintenance windows in ElastiCache?

    <p>To perform software patching</p> Signup and view all the answers

    What is a characteristic of ElastiCache nodes?

    <p>They are a collection of nodes using the same caching engine</p> Signup and view all the answers

    How is access to ElastiCache nodes controlled when not using a VPC?

    <p>Using Cache Security Groups</p> Signup and view all the answers

    What is a key use case for ElastiCache?

    <p>Offloading reads from a database and storing the results of computations</p> Signup and view all the answers

    What is the minimum scope of an ElastiCache cluster?

    <p>Multiple nodes in the same subnet</p> Signup and view all the answers

    What is a limitation of ElastiCache Memcached?

    <p>It does not support automatic failover</p> Signup and view all the answers

    What is a key use case for ElastiCache?

    <p>Storing session state data</p> Signup and view all the answers

    What is the purpose of Redis shards in ElastiCache?

    <p>To distribute data across multiple nodes</p> Signup and view all the answers

    What is the billing model for ElastiCache?

    <p>Billed by node size and hours of use</p> Signup and view all the answers

    What is the primary purpose of Redis replication in ElastiCache?

    <p>To provide high availability across multiple AZs</p> Signup and view all the answers

    What is the primary purpose of Lazy Loading caching strategy?

    <p>To load data into the cache when it is requested</p> Signup and view all the answers

    What is the primary purpose of Write-Through caching strategy?

    <p>To write data to the cache and the underlying database simultaneously</p> Signup and view all the answers

    What metric should be monitored to detect possible issues with the application behavior?

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

    What is the purpose of the MemoryFragmentationRatio metric in ElastiCache Redis?

    <p>To analyze the efficiency of memory allocation</p> Signup and view all the answers

    How does AWS CloudTrail help with security in ElastiCache?

    <p>By logging every event or request</p> Signup and view all the answers

    What determines the pricing of ElastiCache?

    <p>Node-hour consumed for each Node Type</p> Signup and view all the answers

    What is the purpose of the Evictions metric in ElastiCache Memcached?

    <p>To detect when to scale up or out</p> Signup and view all the answers

    What is the advantage of using Redis Auth with ElastiCache Redis?

    <p>Improved data security</p> Signup and view all the answers

    What type of metric is CPUUtilization in ElastiCache Memcached?

    <p>Host-level metric</p> Signup and view all the answers

    What is the recommended action if the SwapUsage metric exceeds 50 MB?

    <p>Increase the ConnectionOverhead parameter value</p> Signup and view all the answers

    What is the purpose of the CacheHitRate metric in ElastiCache Redis?

    <p>To indicate the usage efficiency of the Redis instance</p> Signup and view all the answers

    What is the unit of billing for ElastiCache?

    <p>Node-hour consumed for each Node Type</p> Signup and view all the answers

    What is the primary purpose of ElastiCache?

    <p>To offload reads from a database and store the results of computations</p> Signup and view all the answers

    What is the key difference between Lazy Loading and Write-Through caching strategies?

    <p>Lazy Loading loads data only when requested, while Write-Through loads data when written</p> Signup and view all the answers

    What is a limitation of ElastiCache Memcached?

    <p>It does not support multi-AZ failover or replication</p> Signup and view all the answers

    What is the maximum number of nodes per region for Memcached?

    <p>100</p> Signup and view all the answers

    What is the primary purpose of Redis shards?

    <p>To provide a primary node and read replicas</p> Signup and view all the answers

    What is the purpose of maintenance windows in ElastiCache?

    <p>To perform software patching</p> Signup and view all the answers

    What is a key characteristic of ElastiCache nodes?

    <p>They are in-memory caches</p> Signup and view all the answers

    What is a primary feature of ElastiCache Memcached compared to Redis?

    <p>Simplest model and ability to run large nodes</p> Signup and view all the answers

    What is the primary purpose of Redis replication?

    <p>To provide high availability and fault tolerance</p> Signup and view all the answers

    What is a common use case for ElastiCache in terms of application data?

    <p>Storing user session state</p> Signup and view all the answers

    What does the CPUUtilization metric measure in ElastiCache Memcached?

    <p>The percentage of CPU used by the host</p> Signup and view all the answers

    What can you do to address a high Evictions metric in ElastiCache Memcached?

    <p>Scale your cluster up by using a larger node type or scale out by adding more nodes</p> Signup and view all the answers

    What is the purpose of logging and auditing in Amazon ElastiCache?

    <p>To identify who generated a request and determine access to AWS resources</p> Signup and view all the answers

    What is the unit of pricing for ElastiCache?

    <p>Per Node-hour consumed</p> Signup and view all the answers

    What is the purpose of Redis Auth in Amazon ElastiCache?

    <p>To require a token with ElastiCache Redis</p> Signup and view all the answers

    What does the EngineCPUUtilization metric measure in ElastiCache Redis?

    <p>The percentage of CPU used by the Redis engine thread</p> Signup and view all the answers

    What is the purpose of the CacheHits metric in ElastiCache Redis?

    <p>To measure the number of successful read-only key lookups</p> Signup and view all the answers

    What is not charged in ElastiCache?

    <p>Data transfer between Amazon EC2 and Amazon ElastiCache within the same Availability Zone</p> Signup and view all the answers

    What is a characteristic of ElastiCache high availability?

    <p>It uses multiple cache nodes</p> Signup and view all the answers

    What does the MemoryFragmentationRatio metric indicate in ElastiCache Redis?

    <p>The efficiency in the allocation of memory of the Redis engine</p> Signup and view all the answers

    What is the smallest building block of ElastiCache?

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

    What type of workloads is ElastiCache particularly suited for?

    <p>Read-heavy application workloads</p> Signup and view all the answers

    How are ElastiCache nodes deployed within a VPC regulated?

    <p>Via Subnet groups</p> Signup and view all the answers

    What is the billing model for ElastiCache based on?

    <p>Node size and hours of use</p> Signup and view all the answers

    What happens to failed nodes in ElastiCache?

    <p>They are automatically replaced</p> Signup and view all the answers

    Which statement is true regarding ElastiCache's data storage characteristics?

    <p>Data is not persistent in the traditional sense</p> Signup and view all the answers

    Which of the following accurately describes the accessibility of ElastiCache nodes?

    <p>Accessible only by EC2 instances within the same VPC</p> Signup and view all the answers

    What is a common use for cached information in ElastiCache?

    <p>Storing the results of I/O-intensive database queries</p> Signup and view all the answers

    What must be configured when deploying ElastiCache within a VPC?

    <p>Subnet groups for the ElastiCache cluster</p> Signup and view all the answers

    What type of ElastiCache instances are available besides on-demand?

    <p>Reserved instances</p> Signup and view all the answers

    What is the primary benefit of using ElastiCache for read-heavy application workloads or compute-intensive workloads?

    <p>Significantly improved latency and throughput</p> Signup and view all the answers

    What is a characteristic of ElastiCache nodes?

    <p>Fixed-sized chunk of secure, network-attached RAM</p> Signup and view all the answers

    What is the purpose of subnet groups in ElastiCache?

    <p>To designate subnets for an Amazon ElastiCache Cluster</p> Signup and view all the answers

    What happens when an ElastiCache node fails?

    <p>Failed nodes are automatically replaced</p> Signup and view all the answers

    What type of instance can be used for ElastiCache?

    <p>On-demand or reserved instances</p> Signup and view all the answers

    What is a common use case for ElastiCache?

    <p>Storing session state</p> Signup and view all the answers

    What is a limitation of ElastiCache?

    <p>ElastiCache EC2 nodes cannot be accessed from the Internet, nor can they be accessed by EC2 instances in other VPCs</p> Signup and view all the answers

    How is access to ElastiCache nodes controlled when deployed in a VPC?

    <p>Using VPC security groups and subnet groups</p> Signup and view all the answers

    What is a characteristic of ElastiCache?

    <p>In-memory key/value store</p> Signup and view all the answers

    What is the main difference between Memcached and Redis engines in ElastiCache?

    <p>Redis supports more complex data structures, while Memcached does not</p> Signup and view all the answers

    What is the billing model for ElastiCache?

    <p>Node size and hours of use</p> Signup and view all the answers

    What is the purpose of maintenance windows in ElastiCache?

    <p>To perform software patching</p> Signup and view all the answers

    What is a limitation of ElastiCache Memcached?

    <p>It does not support multi-AZ failover or replication</p> Signup and view all the answers

    What is the maximum number of nodes per region for Memcached?

    <p>100</p> Signup and view all the answers

    What is the purpose of Redis shards?

    <p>To distribute replicas across availability zones</p> Signup and view all the answers

    What is the primary purpose of Redis replication?

    <p>To provide automatic failover</p> Signup and view all the answers

    What is the difference between Lazy Loading and Write-Through caching strategies?

    <p>Lazy Loading loads data when requested, while Write-Through loads data in advance</p> Signup and view all the answers

    What is a key use case for ElastiCache?

    <p>Offloading reads from a database</p> Signup and view all the answers

    What happens when an existing ElastiCache Cluster is moved outside of a VPC?

    <p>The cluster becomes unavailable</p> Signup and view all the answers

    What is a characteristic of ElastiCache nodes?

    <p>They can span multiple availability zones</p> Signup and view all the answers

    What metric is used to evaluate the efficiency of memory allocation in the Redis engine?

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

    What is the recommended approach for addressing a high SwapUsage metric in ElastiCache Memcached?

    <p>Increase the ConnectionOverhead parameter.</p> Signup and view all the answers

    Which metric indicates the percentage of successful read-only key lookups in the Redis engine?

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

    What is the primary purpose of Redis Auth?

    <p>To authenticate client connections to ElastiCache Redis instances.</p> Signup and view all the answers

    What is the recommended approach for handling an increasing number of CurrConnections in ElastiCache Memcached?

    <p>Investigate the application behavior.</p> Signup and view all the answers

    What is the primary purpose of AWS CloudTrail in relation to ElastiCache?

    <p>To log all ElastiCache actions and events.</p> Signup and view all the answers

    What is the recommended action if the Evictions metric exceeds a predefined threshold in ElastiCache Memcached?

    <p>Increase the cache node size or add more nodes.</p> Signup and view all the answers

    How is the pricing for ElastiCache calculated?

    <p>Based on the number of node-hours consumed by each node type.</p> Signup and view all the answers

    What is the recommended value for the MemoryFragmentationRatio metric in ElastiCache Redis?

    <p>Above 1.0</p> Signup and view all the answers

    Which of the following metrics is unique to ElastiCache Redis, not found in Memcached?

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

    Study Notes

    Overview of ElastiCache

    • Fully managed service for Redis and Memcached in-memory data stores.
    • Used to enhance latency and throughput for read-heavy and compute-intensive workloads.
    • Ideal for Online Analytics Processing (OLAP) transactions.
    • Operates on a push-button scalability model for memory, writes, and reads.

    Access and Security

    • ElastiCache nodes are accessible only through VPC security groups and subnet groups.
    • Nodes cannot be accessed from the internet or EC2 instances in other VPCs.
    • Access outside of VPC utilizes Cache Security Groups linked to EC2 Security Groups.

    Node and Cluster Configuration

    • A node is a fixed-size, network-attached RAM unit, running either Memcached or Redis.
    • Each node has a unique DNS name and port, with automatic replacement for failed nodes.
    • Nodes can be deployed in clusters, spanning multiple subnets within the same group.

    Use Cases

    • Commonly used for offloading reads from databases and storing computational results and session states.
    • ElastiCache can manage on-demand or reserved instances but not Spot instances.

    Memcached Features

    • Simplistic model for large nodes and scaling capabilities.
    • Multi-threaded, supporting 1-20 nodes per cluster and max 100 nodes per region.
    • Lacks support for multi-AZ failover, replication, and snapshots.
    • Ideal for caching database objects and integrating with features like SNS for notifications.

    Redis Features

    • Open-source and supports complex data structures, providing persistent data storage.
    • Not multi-threaded; scales through shard addition rather than node addition.
    • Offers automatic failover, master/slave replication, and multi-AZ redundancy.
    • Supports snapshots for backups, allowing for data restoration.

    Clustering Modes in Redis

    • Disabled Clustering Mode:
      • One shard can contain a primary node and multiple read-only replicas.
    • Enabled Clustering Mode:
      • Up to 15 shards, each with primary and read-only replicas; enables better scalability.

    Failure Handling

    • ElastiCache detects failures and promotes replicas with the lowest lag to primary status.
    • DNS records are updated to point to the new primary node automatically.

    Caching Strategies

    • Lazy Loading: Load data into the cache only when it's requested.
    • Write-Through: Updates data in the cache as it's written to the database, ensuring no stale data.

    Monitoring and Metrics

    • Memcached Metrics:
      • CPU Utilization, Swap Usage, Evictions, and Current Connections provide insights into performance.
    • Redis Metrics:
      • Include Engine CPU Utilization, Memory Fragmentation Ratio, Cache Hits/Misses, and Current Connections.

    Logging and Auditing

    • Amazon ElastiCache actions are logged via AWS CloudTrail, tracking request identity and permissions.
    • Redis supports authentication tokens to enhance security.

    Pricing

    • Charged per node-hour for each node type, with partial hours billed as full hours.
    • No charges for data transfer between EC2 and ElastiCache within the same Availability Zone.

    Key Distinctions between Memcached and Redis

    • Memcached excels in simple object caching, while Redis offers more complex data structure support and persistence.
    • Redis allows for fault tolerance through multi-AZ and replication features; Memcached does not support these capabilities.

    Overview of ElastiCache

    • Fully managed service for Redis and Memcached in-memory data stores.
    • Used to enhance latency and throughput for read-heavy and compute-intensive workloads.
    • Ideal for Online Analytics Processing (OLAP) transactions.
    • Operates on a push-button scalability model for memory, writes, and reads.

    Access and Security

    • ElastiCache nodes are accessible only through VPC security groups and subnet groups.
    • Nodes cannot be accessed from the internet or EC2 instances in other VPCs.
    • Access outside of VPC utilizes Cache Security Groups linked to EC2 Security Groups.

    Node and Cluster Configuration

    • A node is a fixed-size, network-attached RAM unit, running either Memcached or Redis.
    • Each node has a unique DNS name and port, with automatic replacement for failed nodes.
    • Nodes can be deployed in clusters, spanning multiple subnets within the same group.

    Use Cases

    • Commonly used for offloading reads from databases and storing computational results and session states.
    • ElastiCache can manage on-demand or reserved instances but not Spot instances.

    Memcached Features

    • Simplistic model for large nodes and scaling capabilities.
    • Multi-threaded, supporting 1-20 nodes per cluster and max 100 nodes per region.
    • Lacks support for multi-AZ failover, replication, and snapshots.
    • Ideal for caching database objects and integrating with features like SNS for notifications.

    Redis Features

    • Open-source and supports complex data structures, providing persistent data storage.
    • Not multi-threaded; scales through shard addition rather than node addition.
    • Offers automatic failover, master/slave replication, and multi-AZ redundancy.
    • Supports snapshots for backups, allowing for data restoration.

    Clustering Modes in Redis

    • Disabled Clustering Mode:
      • One shard can contain a primary node and multiple read-only replicas.
    • Enabled Clustering Mode:
      • Up to 15 shards, each with primary and read-only replicas; enables better scalability.

    Failure Handling

    • ElastiCache detects failures and promotes replicas with the lowest lag to primary status.
    • DNS records are updated to point to the new primary node automatically.

    Caching Strategies

    • Lazy Loading: Load data into the cache only when it's requested.
    • Write-Through: Updates data in the cache as it's written to the database, ensuring no stale data.

    Monitoring and Metrics

    • Memcached Metrics:
      • CPU Utilization, Swap Usage, Evictions, and Current Connections provide insights into performance.
    • Redis Metrics:
      • Include Engine CPU Utilization, Memory Fragmentation Ratio, Cache Hits/Misses, and Current Connections.

    Logging and Auditing

    • Amazon ElastiCache actions are logged via AWS CloudTrail, tracking request identity and permissions.
    • Redis supports authentication tokens to enhance security.

    Pricing

    • Charged per node-hour for each node type, with partial hours billed as full hours.
    • No charges for data transfer between EC2 and ElastiCache within the same Availability Zone.

    Key Distinctions between Memcached and Redis

    • Memcached excels in simple object caching, while Redis offers more complex data structure support and persistence.
    • Redis allows for fault tolerance through multi-AZ and replication features; Memcached does not support these capabilities.

    Overview of ElastiCache

    • Fully managed service for Redis and Memcached in-memory data stores.
    • Used to enhance latency and throughput for read-heavy and compute-intensive workloads.
    • Ideal for Online Analytics Processing (OLAP) transactions.
    • Operates on a push-button scalability model for memory, writes, and reads.

    Access and Security

    • ElastiCache nodes are accessible only through VPC security groups and subnet groups.
    • Nodes cannot be accessed from the internet or EC2 instances in other VPCs.
    • Access outside of VPC utilizes Cache Security Groups linked to EC2 Security Groups.

    Node and Cluster Configuration

    • A node is a fixed-size, network-attached RAM unit, running either Memcached or Redis.
    • Each node has a unique DNS name and port, with automatic replacement for failed nodes.
    • Nodes can be deployed in clusters, spanning multiple subnets within the same group.

    Use Cases

    • Commonly used for offloading reads from databases and storing computational results and session states.
    • ElastiCache can manage on-demand or reserved instances but not Spot instances.

    Memcached Features

    • Simplistic model for large nodes and scaling capabilities.
    • Multi-threaded, supporting 1-20 nodes per cluster and max 100 nodes per region.
    • Lacks support for multi-AZ failover, replication, and snapshots.
    • Ideal for caching database objects and integrating with features like SNS for notifications.

    Redis Features

    • Open-source and supports complex data structures, providing persistent data storage.
    • Not multi-threaded; scales through shard addition rather than node addition.
    • Offers automatic failover, master/slave replication, and multi-AZ redundancy.
    • Supports snapshots for backups, allowing for data restoration.

    Clustering Modes in Redis

    • Disabled Clustering Mode:
      • One shard can contain a primary node and multiple read-only replicas.
    • Enabled Clustering Mode:
      • Up to 15 shards, each with primary and read-only replicas; enables better scalability.

    Failure Handling

    • ElastiCache detects failures and promotes replicas with the lowest lag to primary status.
    • DNS records are updated to point to the new primary node automatically.

    Caching Strategies

    • Lazy Loading: Load data into the cache only when it's requested.
    • Write-Through: Updates data in the cache as it's written to the database, ensuring no stale data.

    Monitoring and Metrics

    • Memcached Metrics:
      • CPU Utilization, Swap Usage, Evictions, and Current Connections provide insights into performance.
    • Redis Metrics:
      • Include Engine CPU Utilization, Memory Fragmentation Ratio, Cache Hits/Misses, and Current Connections.

    Logging and Auditing

    • Amazon ElastiCache actions are logged via AWS CloudTrail, tracking request identity and permissions.
    • Redis supports authentication tokens to enhance security.

    Pricing

    • Charged per node-hour for each node type, with partial hours billed as full hours.
    • No charges for data transfer between EC2 and ElastiCache within the same Availability Zone.

    Key Distinctions between Memcached and Redis

    • Memcached excels in simple object caching, while Redis offers more complex data structure support and persistence.
    • Redis allows for fault tolerance through multi-AZ and replication features; Memcached does not support these capabilities.

    Overview of ElastiCache

    • Fully managed service for Redis and Memcached in-memory data stores.
    • Used to enhance latency and throughput for read-heavy and compute-intensive workloads.
    • Ideal for Online Analytics Processing (OLAP) transactions.
    • Operates on a push-button scalability model for memory, writes, and reads.

    Access and Security

    • ElastiCache nodes are accessible only through VPC security groups and subnet groups.
    • Nodes cannot be accessed from the internet or EC2 instances in other VPCs.
    • Access outside of VPC utilizes Cache Security Groups linked to EC2 Security Groups.

    Node and Cluster Configuration

    • A node is a fixed-size, network-attached RAM unit, running either Memcached or Redis.
    • Each node has a unique DNS name and port, with automatic replacement for failed nodes.
    • Nodes can be deployed in clusters, spanning multiple subnets within the same group.

    Use Cases

    • Commonly used for offloading reads from databases and storing computational results and session states.
    • ElastiCache can manage on-demand or reserved instances but not Spot instances.

    Memcached Features

    • Simplistic model for large nodes and scaling capabilities.
    • Multi-threaded, supporting 1-20 nodes per cluster and max 100 nodes per region.
    • Lacks support for multi-AZ failover, replication, and snapshots.
    • Ideal for caching database objects and integrating with features like SNS for notifications.

    Redis Features

    • Open-source and supports complex data structures, providing persistent data storage.
    • Not multi-threaded; scales through shard addition rather than node addition.
    • Offers automatic failover, master/slave replication, and multi-AZ redundancy.
    • Supports snapshots for backups, allowing for data restoration.

    Clustering Modes in Redis

    • Disabled Clustering Mode:
      • One shard can contain a primary node and multiple read-only replicas.
    • Enabled Clustering Mode:
      • Up to 15 shards, each with primary and read-only replicas; enables better scalability.

    Failure Handling

    • ElastiCache detects failures and promotes replicas with the lowest lag to primary status.
    • DNS records are updated to point to the new primary node automatically.

    Caching Strategies

    • Lazy Loading: Load data into the cache only when it's requested.
    • Write-Through: Updates data in the cache as it's written to the database, ensuring no stale data.

    Monitoring and Metrics

    • Memcached Metrics:
      • CPU Utilization, Swap Usage, Evictions, and Current Connections provide insights into performance.
    • Redis Metrics:
      • Include Engine CPU Utilization, Memory Fragmentation Ratio, Cache Hits/Misses, and Current Connections.

    Logging and Auditing

    • Amazon ElastiCache actions are logged via AWS CloudTrail, tracking request identity and permissions.
    • Redis supports authentication tokens to enhance security.

    Pricing

    • Charged per node-hour for each node type, with partial hours billed as full hours.
    • No charges for data transfer between EC2 and ElastiCache within the same Availability Zone.

    Key Distinctions between Memcached and Redis

    • Memcached excels in simple object caching, while Redis offers more complex data structure support and persistence.
    • Redis allows for fault tolerance through multi-AZ and replication features; Memcached does not support these capabilities.

    Overview of ElastiCache

    • Fully managed service for Redis and Memcached in-memory data stores.
    • Used to enhance latency and throughput for read-heavy and compute-intensive workloads.
    • Ideal for Online Analytics Processing (OLAP) transactions.
    • Operates on a push-button scalability model for memory, writes, and reads.

    Access and Security

    • ElastiCache nodes are accessible only through VPC security groups and subnet groups.
    • Nodes cannot be accessed from the internet or EC2 instances in other VPCs.
    • Access outside of VPC utilizes Cache Security Groups linked to EC2 Security Groups.

    Node and Cluster Configuration

    • A node is a fixed-size, network-attached RAM unit, running either Memcached or Redis.
    • Each node has a unique DNS name and port, with automatic replacement for failed nodes.
    • Nodes can be deployed in clusters, spanning multiple subnets within the same group.

    Use Cases

    • Commonly used for offloading reads from databases and storing computational results and session states.
    • ElastiCache can manage on-demand or reserved instances but not Spot instances.

    Memcached Features

    • Simplistic model for large nodes and scaling capabilities.
    • Multi-threaded, supporting 1-20 nodes per cluster and max 100 nodes per region.
    • Lacks support for multi-AZ failover, replication, and snapshots.
    • Ideal for caching database objects and integrating with features like SNS for notifications.

    Redis Features

    • Open-source and supports complex data structures, providing persistent data storage.
    • Not multi-threaded; scales through shard addition rather than node addition.
    • Offers automatic failover, master/slave replication, and multi-AZ redundancy.
    • Supports snapshots for backups, allowing for data restoration.

    Clustering Modes in Redis

    • Disabled Clustering Mode:
      • One shard can contain a primary node and multiple read-only replicas.
    • Enabled Clustering Mode:
      • Up to 15 shards, each with primary and read-only replicas; enables better scalability.

    Failure Handling

    • ElastiCache detects failures and promotes replicas with the lowest lag to primary status.
    • DNS records are updated to point to the new primary node automatically.

    Caching Strategies

    • Lazy Loading: Load data into the cache only when it's requested.
    • Write-Through: Updates data in the cache as it's written to the database, ensuring no stale data.

    Monitoring and Metrics

    • Memcached Metrics:
      • CPU Utilization, Swap Usage, Evictions, and Current Connections provide insights into performance.
    • Redis Metrics:
      • Include Engine CPU Utilization, Memory Fragmentation Ratio, Cache Hits/Misses, and Current Connections.

    Logging and Auditing

    • Amazon ElastiCache actions are logged via AWS CloudTrail, tracking request identity and permissions.
    • Redis supports authentication tokens to enhance security.

    Pricing

    • Charged per node-hour for each node type, with partial hours billed as full hours.
    • No charges for data transfer between EC2 and ElastiCache within the same Availability Zone.

    Key Distinctions between Memcached and Redis

    • Memcached excels in simple object caching, while Redis offers more complex data structure support and persistence.
    • Redis allows for fault tolerance through multi-AZ and replication features; Memcached does not support these capabilities.

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    Description

    Learn about Amazon ElastiCache, a web service that provides in-memory data stores for Redis and Memcached protocols, improving latency and throughput for read-heavy workloads.

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