Replay exposes practical differences

Unit tests prove policy logic. Synthetic tests prove expected paths. Traffic replay shows how real consumers behave: unusual headers, missing optional fields, retry storms, slow backends, unexpected methods, and odd token patterns. For Apigee migration, replay can reveal differences that documentation will not.

How to use it

Replay should focus on representative traffic, high-value APIs, and edge cases that matter operationally. Scrub sensitive data, protect backend systems, and compare target responses against source behavior. Differences should be triaged as acceptable change, target defect, source defect, or consumer communication item.

Metrics to compare

  • Status code distribution and error payloads.
  • Latency by proxy and target.
  • OAuth failure modes.
  • Quota, spike arrest, and security policy behavior.

Replay is valuable because it turns migration confidence into evidence.