API Deprecation and Sunset Runbook
For backend teams, one of the most difficult operational tasks is not creating a new API, but safely removing an old one. Poorly handled deprecations can trigger customer outages, mobile regressions, and partner escalations. That is why API sunset work should be treated as an operational contract, not just a documentation note.
Define the contract before the code change
At minimum, teams should agree on:
- deprecation announcement date
- warning phase start
- new-client cut-off date
- full shutdown date
Without these milestones, different teams interpret the same sunset differently.
Identify real users through traffic first
Do not retire based only on aggregate volume.
- which client versions still use it
- which tenants depend on it
- what the business impact is if it breaks
Low volume can still mean high importance.
Increase pressure gradually
A safer pattern is usually:
- mark as deprecated in docs
- emit warning headers and logs
- block new consumers
- partially fail or redirect traffic
- fully disable
Conclusion
API sunset work is as much about relationships as it is about code. Strong teams do not let old endpoints live forever, but they also do not cut them off abruptly. They use observability, staged pressure, and explicit timelines.
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