A just-deployed App Service release is causing production errors and needs an immediate rollback. Is swapping back to the previous slot genuinely faster than redeploying the old package?

If the previous version is still sitting untouched in the slot you swapped from, swapping back is almost always faster and safer — it's a near-instant, already-tested cutover rather than a fresh deployment with its own risk of something going wrong mid-redeploy. It stops being the better option the moment that slot has already been reused for the next release or otherwise modified, at which point the "previous version" isn't actually there to swap back to anymore, and a direct redeploy of a known-good build becomes the real fastest path.

The advantage of swap-back isn't inherent to slots as a mechanism — it's entirely conditional on the previous version still genuinely being present and untouched in the slot being swapped from.

• Swap-back is fast and low-risk specifically because it's not a new deployment at all — it's repointing production traffic to code that was already running and already validated moments earlier.
• The moment the source slot has been reused for the next release, swap-back no longer restores the previous version — the team needs to already know this before an incident, not discover it during one.
• A direct redeploy of a known-good build artifact is the correct fallback when swap-back isn't available, and it should have a documented, practiced path — not be improvised for the first time during an incident.
• Preserving the previous version in its slot until a release is confirmed stable is a deliberate operational discipline, not an automatic property of using deployment slots.

• Azure App Service: Set up staging environments