Is DynamoDB in-memory?

No. DynamoDB is not an in-memory database — every write is persisted to durable storage and automatically replicated across three Availability Zones. When you need in-memory speed, DynamoDB Accelerator (DAX) adds a fully managed in-memory cache that cuts eventually consistent reads from single-digit milliseconds to microseconds.

Durable by design

DynamoDB is a durable operational database: writes are stored on durable media and replicated across three Availability Zones by default, backing a 99.99% availability SLA. That's the opposite trade-off from a pure in-memory store, where data lives in RAM and durability is optional.

It's still fast without a cache

Baseline DynamoDB delivers consistent single-digit-millisecond reads and writes at any scale, because every read targets a partition key directly instead of scanning. Most workloads never need a cache at all.

DAX: the in-memory layer

When microseconds matter — real-time bidding, gaming leaderboards, hot product pages — DAX is AWS's answer: a DynamoDB-compatible, write-through, in-memory cache that improves eventually consistent read performance by an order of magnitude with minimal code changes. It's not a fit for strongly consistent reads or write-intensive workloads. If you're weighing DynamoDB against a true in-memory store, DynamoDB vs Redis compares durability, speed, and cost directly.

Go deeper

Understand the consistency trade-offs in the consistency guide, see can DynamoDB be used as a cache? for the inverse question, estimate read costs with the pricing calculator, and download DynoTable to inspect your tables.

References

Last verified 2026-07-13 against the official AWS documentation linked above.