Quick answer
Lambda synchronous requests and ordinary responses allow 6 MB each. Streamed synchronous responses can reach 200 MB, while asynchronous invocation payloads are limited to 1 MB.
Verified Sep 17, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| Synchronous request and responseAWS uses MB in Lambda docs to mean 1,024 KB. | 6 MB each | Synchronous invocation | Amazon Web ServicesSep 17, 2026 |
| Streamed synchronous responseBandwidth is uncapped for the first 6 MB and limited for the remainder according to AWS documentation. | 200 MB | Streamed synchronous response | Amazon Web ServicesSep 17, 2026 |
| Asynchronous invocation payloadSmaller than the synchronous request/response constraint. | 1 MB | Asynchronous invocation | Amazon Web ServicesSep 17, 2026 |
Why does this limit matter?
The correct limit depends on invocation mode, so one number cannot accurately describe every Lambda payload.
API Gateway, event sources, SDKs, and destinations can impose their own smaller constraints.
What should you check?
- Identify synchronous, asynchronous, or response-streaming invocation mode.
- Measure the serialized event or response, not the in-memory object.
- Check the invoking and downstream services for lower payload caps.
Important caveats
- AWS Lambda documentation uses MB to mean 1,024 KB.
- Streamed response bandwidth changes after the initial portion of the response.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
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