Start here. This is the direct spoken answer to practice first.
Why this question matters
Staging and production must differ in environment-owned values without drifting in required structure or unintended settings. A release-time configuration snapshot and clear slot-stickiness rules make those differences explainable and reversible.
I would compare staging and production settings at the time of the failure: app settings, connection strings, Key Vault references, feature flags, managed identity, allowed origins, auth callbacks, and runtime stack. Then I would identify which values are meant to be slot-specific and which are accidental drift. I would check the deployment record and recent manual changes because config drift often comes from emergency portal edits. The immediate fix depends on whether production needs a corrected setting, swap-back, or feature disablement.