📨 Messaging Advanced ⏱️ 9 min

Migrating NATS Event Contracts Without Breaking Consumers

A practical strategy for evolving NATS subjects and event naming while keeping producers and consumers compatible during transition windows.

By Victor Robin • • Updated:
natsevent-drivencontractsworkersmigration

Introduction

Event names are contracts. BlueRobin recently migrated subject semantics and split processing subjects, which required careful compatibility handling across API, workers, and web notifier paths.

Commit Signals

  • 8afa106: split document processing subjects and fixed notifier tests.
  • e8d8532 (blog): renamed upload wording to OCR requested naming.

Migration Pattern

  1. Introduce provider-driven subject resolution.
  2. Keep old/new subjects in a transition window.
  3. Add contract tests around publish/subscribe paths.
  4. Remove legacy constants after consumers converge.

Conclusion

Contract migrations work when naming, rollout windows, and tests are treated as one delivery unit.

Related reading:

  • /telegram-nats-notification-flow/
  • /nats-kv-idempotent-workers-cas/