# Lambda durable functions

> Per-step retries in plain code, inside Lambda. A candidate fix for hand-tuned SQS retry pain.

- Verdict: Watching (Proposed: research-backed, not yet confirmed by Nic)
- Vendor: AWS
- Layer: [APIs, queues and events](https://cloudlesslabs.com/stack/layers/api-events.md). Job: Durable multi-step jobs
- Last reviewed: 18 October 2026, by Nicolas Dao (Cloudless Labs, Sydney)
- Web page: https://cloudlesslabs.com/stack/aws-lambda-durable-functions/. The whole stack in one file: https://cloudlesslabs.com/stack/brief.md

Launched December 2025 and available in Sydney. It solves a real pain of mine: tuning SQS visibility timeouts and DLQs so a flaky third step doesn't rerun the first two. Worth a pilot.

## Use it when

- A job has several steps calling flaky services, and a failure shouldn't rerun the steps that already succeeded.

## Don't use it when

- A single-step job: SQS + Lambda is cheaper and simpler.
- An SQS-triggered run that would exceed 15 minutes in total.

## Pricing

Example: 1M runs a month of receive → enrich via a flaky API → write Postgres → notify ≈ $47, vs ~$10 for SQS + one Lambda (where a failure reruns every step) and ~$110 for Step Functions Standard.

## Gotchas, with fixes

- **Gotcha:** Whether retries are billed as extra operations isn't verified.
  **Fix:** Pilot on one workload and read the bill before rolling out.

## Provisioning

Official Pulumi package · Official Terraform provider

Configured on the Lambda function in @pulumi/aws (verify the exact properties before use).

## Instead, consider

- [Amazon SQS](https://cloudlesslabs.com/stack/aws-sqs/index.md): Simple one-step jobs.
- [AWS Step Functions](https://cloudlesslabs.com/stack/aws-step-functions/index.md): Never, for me.

## Where it fits

- [Background jobs and retries](https://cloudlesslabs.com/stack/use-cases/background.md): pick 4. Watching, for multi-step jobs with flaky dependencies.

## In The Stack Weekly

- [Week 43: Lambda durable functions](https://cloudlesslabs.com/weekly/2026-w43/index.md), worth a pilot

## Sources

- [Lambda durable functions](https://docs.aws.amazon.com/lambda/latest/dg/durable-functions.html)

## Related

- [APIs, queues and events](https://cloudlesslabs.com/stack/layers/api-events.md): every tool in this layer, with its verdict
- [The whole stack in one file](https://cloudlesslabs.com/stack/brief.md): every use case and tool, for questions that span many
- [Map of every Markdown file on cloudlesslabs.com, with what each one answers](https://ask.cloudlesslabs.com)