AWS ElastiCache Exam Tips for Redis & Memcached

AWS ElastiCache Exam Preparation

ElastiCache – In-memory Data store. For high performance and low latency data retrieval.Write and memory scaling is supported with sharding, Replicas provide read scaling.

  • Amazon ElastiCache can automatically detect and recover from the failure of a
    cache node.
  • Types:
    • Memcached (supports adding nodes)
      • Memcached provides a very simple interface that allows you to write and read objects into in-memory key/value data stores.
      • Use case – where frequently accessed data must be in-memory,Web, Mobile Apps, Gaming, Ad-Tech, and E-Commerce.
      • The default limit is 20 nodes per cluster.
    • Security & Encryption

      • ElastiCache for Redis In-Transit Encryption (TLS) – In-transit encryption is optional and can only be enabled on Redis replication groups when they are created. You enable in-transit encryption on a replication group by setting the parameter TransitEncryptionEnabled to true.
      • ElastiCache for Redis At-Rest Encryption – When ElastiCache for Redis at-rest encryption is enabled on a replication group, your data is encrypted when it’s on the disk during sync and backup operations
      • Authenticating Users with Redis AUTH – Using Redis Auth command can improve data security by requiring the user to enter a password before they are granted permission to execute Redis commands on a password-protected Redis server.
    • Multi-AZ with Automatic Failover
      • You can enable Multi-AZ with Automatic Failover on your Redis cluster.
      • Improves your fault tolerance in those cases where your cluster’s read/write primary cluster becomes unreachable or fails for any reason.
      • Multi-AZ with automatic failover is only supported on Redis clusters that support replication
    • Exam Tips:
      • If you have any questions on dynamic web application requiring High performance.High-performance, distributed memory object caching system, intended for use in speeding up dynamic web applications –> Recommend Elasticache.
      • Memcache supports horizontal scaling (adding or removing nodes) & Limited Vertical scaling.
      • Memcached are standalone in-memory services without any redundant data protection services, ephemeral.
      • Snapshots cannot be created for clusters using the Memcached engine because it is a purely in-memory key. — If snapshot is in question then prefer Redis.
      • Use Memcached when you need a simple,in-memory object store that can be easily partitioned.
    • Redis (support multi AZ with Replicas)
      • Use Casedatabase cache and message broker /queue.
      • Redis engine, Amazon ElastiCache makes it easy to set up read replicas and fail over from the primary to a replica in the event of a problem.
      • Redis clusters also can support up to five read replicas to offload read requests.
      • Single node, unlike Memcached which supports 20 nodes.
    • Exam Tips:
      • when Caching and Data persistence in question then choose Redis. Unlike Memcached, Redis supports the ability to persist the in-memory data onto disk.
      • Redis allows you to create snapshots that back up your data and then recover or replicate from the backups but not Memcached.
      • If you see Sort and Rank Data, use Redis.
      • Horizontal scaling -A replication group consists of up to six clusters, with five of them designated as read replicas.
      • Use Redis when you need to back up and restore your data, need many clones or read replicas.