A DynamoDB table needs queries by an attribute that isn't the partition key, and new query patterns will emerge after launch. Which index type supports this — and what's its key constraint?
A.Local secondary index — addable anytime, any attribute
That's the opposite — LSIs are creation-time only and must share the table's partition key.
B.Global secondary index — any partition/sort key, addable after table creation, with its own provisioned throughput
Correct. GSI = flexible keys + post-creation + own throughput.
C.Local secondary index — any partition key
LSIs reuse the table's partition key — only the sort key changes.
D.A scan with a filter expression — zero setup
Scans work but burn RCU on every item — the expensive fallback.
Why this answer
GSIs let you query by any attributes, can be added after table creation, and consume their own RCU/WCU. LSIs share the table's partition key (only the sort key differs) and must be defined at table creation — a classic exam trap.
Correct answer: B · Last reviewed 2026-10-27
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