DynamoDB vs RDS: Choosing a Database

Match the workload to the right AWS database service.

DynamoDB: serverless NoSQL, single-digit-ms latency, massive scale, key-value / document access patterns.
RDS / Aurora: relational, complex joins, transactions, SQL.
ElastiCache: in-memory caching layer.

Exam tip: unpredictable scale + simple access patterns points to DynamoDB; complex relational queries point to RDS/Aurora.