A cache needs persistence, replication with failover, pub/sub for cache invalidation events, and sorted-set data structures. Which ElastiCache engine?
A.Memcached
Memcached lacks persistence, replication, pub/sub, and complex data types.
B.Redis
Correct — every listed requirement is a Redis differentiator.
C.Either — they are interchangeable
Feature sets differ significantly — persistence and failover alone decide this.
D.DynamoDB DAX instead
DAX accelerates DynamoDB reads specifically — it's not a general cache or pub/sub system.
Why this answer
Redis supports persistence (snapshots/AOF), replication with auto-failover, pub/sub, and rich data structures (sorted sets, lists, hashes). Memcached is a simpler pure in-memory cache — multi-threaded sharding, no persistence, no replication.
Correct answer: B · Last reviewed 2026-11-01
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