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.

0 of 7 readQuiz

DynamoDB Batch Operations: BatchGetItem & BatchWriteItem

DynamoDB BatchGetItem and BatchWriteItem — reading and writing up to 25/100 items per round trip, why batches aren't transactions, and how to handle unprocessed items.

Intermediate5 min read

DynamoDB ReturnValues: Get the Old or New Item From a Write

DynamoDB ReturnValues — how to get the old or new item back from PutItem, UpdateItem and DeleteItem without a second read, the five options, and when each saves a round trip.

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

Enforcing uniqueness on multiple attributes in DynamoDB

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.

Intermediate7 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.