Writes & Operations

Reads get the attention, but writes are where correctness and operational pain live. There's no UPDATE … WHERE that scans, no unique constraint across columns, and no ALTER TABLE to reshape your data. You build those guarantees yourself out of conditional writes and key design.

This section covers the write patterns you'll reach for in production and the operational problems — botched migrations, hot keys — that follow from getting them wrong.

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DynamoDB Batch Operations

DynamoDB batch operations — BatchGetItem reads 100 items per call, BatchWriteItem writes 25, why a batch is not a transaction, and how to retry leftovers.

Intermediate5 min read

How to Delete Multiple Items in DynamoDB

How to delete multiple items in DynamoDB — BatchWriteItem, TransactWriteItems, PartiQL batches and TTL — plus why there is no DELETE ... WHERE statement.

Beginner7 min read

DynamoDB ReturnValues: Get the Old or New Item

DynamoDB ReturnValues hands back the old or new item from PutItem, UpdateItem or DeleteItem without a second read — the five options and when each helps.

Intermediate3 min read

DynamoDB Atomic Counters

How DynamoDB atomic counters work with an ADD update expression, why they aren't idempotent, and when to reach for a conditional update instead.

Intermediate5 min read

DynamoDB Uniqueness on Multiple Attributes

How to enforce a unique constraint on multiple DynamoDB attributes — unique email AND username — with marker items and a condition-guarded TransactWriteItems.

Advanced6 min read

DynamoDB Migrations Without Downtime

DynamoDB migrations without downtime — how to add a new entity type and access pattern to a live table using lazy backfill, online GSIs, and dual-writes.

Advanced6 min read

DynamoDB Hot Partitions

A DynamoDB hot partition is when one partition key absorbs a disproportionate share of traffic and throttles. Here's how to spot it and design it out.

Intermediate8 min read

Knowledge checkTake the quiz

Check what you’ve learned in this section.

Start with atomic counters if you write concurrent updates; jump to migrations if you're staring down a schema change.

Try DynoTable to run conditional writes and watch the results live.