# Cold start latency regression: first 30 minutes checklist

Source: https://releasefailures.com/incidents/cold-start-latency-regression/
Content version: 1.0.0
Verified on: 2026-10-22
Licence: CC BY 4.0

Definition: Serverless or container cold starts become slower after a dependency or image change.
- [ ] FM-01 Compare init duration of cold start invokes before and after the runtime or SDK update, with warm invokes excluded.
- [ ] FM-02 Deploy a copy of an affected function without the SDK import and compare its init duration, to split runtime cost from SDK cost.
- [ ] FM-03 Move the affected functions back to the previous runtime version if their cold start duration breaks the latency budget.
- [ ] FM-04 Check whether the SDK's http handler has a release that loads the http module lazily, and confirm the installed SDK clients are compatible with it.
- [ ] FM-05 Record the runtime version, SDK version and memory setting of every affected function in the incident log.
- [ ] FM-06 Tell owners of latency-sensitive services which runtime version raised cold start duration and by how many milliseconds.
- [ ] FM-07 Open an issue with the runtime or SDK maintainers that includes the minimal repro and the before-and-after init durations.