Querying & Sorting

Reads are where the bill gets written. Query targets one item collection by key; Scan reads the whole table. Reach for Scan with a filter — the SQL instinct — and you pay for every item read, not the few you keep. That's the classic footgun.

This section is about reading efficiently: using the key to do the work, paging correctly, and ordering results with the sort key instead of in-memory sorting.

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Query vs Scan in DynamoDB

Query vs Scan in DynamoDB — Query reads one item collection and bills matched items, Scan reads the whole table before any FilterExpression runs.

Beginner5 min read

Pagination in DynamoDB

How DynamoDB pagination works — loop on LastEvaluatedKey and ExclusiveStartKey, why Limit is not a page size, and how to expose a stateless cursor.

Beginner4 min read

DynamoDB Filtering Strategies

DynamoDB filtering strategies compared — partition key, sort key, sparse indexes, and FilterExpression — and which one actually cuts your read bill.

Intermediate8 min read

Why a DynamoDB Scan Is Slow and Expensive

Why a DynamoDB Scan is slow and expensive, what it actually bills you for, and how to turn a reflexive Scan into a keyed Query that costs a fraction.

Beginner7 min read

DynamoDB Parallel Scans

How DynamoDB parallel scans split a full-table read across workers with Segment and TotalSegments, when they help, and the throughput footgun to avoid.

Advanced7 min read

DynamoDB Sort Key Strategies

DynamoDB sort key strategies for range reads — design a sort key whose byte order matches your read order, so one Query serves many access patterns.

Intermediate8 min read

How to Query DynamoDB in Descending Order

Query DynamoDB in descending order with ScanIndexForward=false — newest-first results, why sorting happens on the sort key, and why reverse reads are free.

Beginner5 min read

Sorting DynamoDB on a Changing Attribute

Sorting DynamoDB on a changing attribute — why a key attribute is immutable, the delete-and-recreate pattern, and moving it to a GSI sort key instead.

Intermediate5 min read

Zero-Padding Sort Keys in DynamoDB

Why "10" sorts before "2" in a DynamoDB string sort key, and how fixed-width zero-padding makes lexicographic byte order match numeric order.

Intermediate5 min read

Knowledge checkTake the quiz

Check what you’ve learned in this section.

Start with Query vs Scan — it's the decision the rest depend on.

Try DynoTable to run these queries against a live table — or compose a full Query/Scan request in the browser with the free query builder.