ElastiCache offers two engines, and the exam tests which to pick based on the features a workload needs.
The difference
Redis supports persistence, replication, automatic failover, and advanced data structures — choose it when you need high availability or richer features. Memcached is simpler, multi-threaded, and purely for caching — choose it for the simplest, horizontally-scalable cache with no persistence needed. Need failover/persistence? Redis. Simple scalable cache? Memcached.
Test yourself
A caching layer needs high availability with automatic failover and data persistence. Which ElastiCache engine?
- Memcached
- Redis
- Neither supports failover
- Both are identical
👉 Click to reveal the answer & explanation
Correct answer: B. Redis supports replication, automatic failover, and persistence — required for high availability. Memcached (A) is a simpler cache without persistence or failover; the other options (C, D) are incorrect.
Related topics
Amazon ElastiCache · Amazon RDS · DynamoDB DAX
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