A product service re-computes the same complex SQL query for every request, and the result changes only hourly. The team wants microsecond-to-millisecond lookups and to relieve the database. What should they add?
A.Amazon ElastiCache (Redis OSS) with a cache-aside (lazy-loading) pattern
Correct. An in-memory cache-aside layer removes repeated expensive queries.
B.A second RDS writer instance
RDS supports one writer; a 'second writer' is not a scaling mechanism (that is what read replicas/Aurora provide differently).
C.S3 Select queries over query-result CSV exports
S3 Select queries files, not a live cache; it adds latency rather than removing it.
D.Larger connection strings to the database
Connection strings do not change query cost.
Why this answer
ElastiCache for Redis provides in-memory lookups in sub-millisecond time. The cache-aside pattern (check cache → on miss, query DB and populate cache) is ideal when the query result changes infrequently.
Correct answer: A · Last reviewed 2026-10-25
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