Asset cache serves old bundle: pre-release and first 30 minutes checklists

Users receive an old JavaScript bundle with a new API and the app errors.

The pre-release checklist maps each item to a test class from the incident page. The first-30-minutes checklist covers detection, containment, the rollback decision and customer communication.

8 pre-release items · 7 first-30-minutes items · verified 2026-10-22

Pre-release checklist

PR-01Scan the build output and fail the release when any JavaScript file URL lacks a content hash in its file name. config
PR-02Confirm the remote entry file is served with a cache header that forces the browser to revalidate it on every load. config
PR-03Confirm the previous deployment's hashed JavaScript assets still return 200 on the server after the new deployment goes live. config
PR-04Confirm the deploy step purges every changed JavaScript chunk at the CDN and fails the deploy when the purge does not complete. config
PR-05Load the app on the previous version in a browser, deploy the new version, reload without a hard refresh and confirm every page widget renders with no JavaScript errors. e2e
PR-06Run the login flow in a browser that still holds the previous deployment's cached chunks and confirm login completes. e2e
PR-07After each deploy, fetch the entry file and every chunk it references through the CDN and alert on any 404 response. synthetic
PR-08After each deploy, run a scripted login from several regions and confirm the chunk hashes it loads match the new build. synthetic

First 30 minutes

FM-01Query frontend asset requests for 404 responses since the last deploy, because existing alerts may not cover them.
FM-02Ask one affected user whether a hard refresh or a cleared browser cache fixes the page.
FM-03Compare the hashes of the entry file and chunks served at the CDN edge with the hashes in the new build.
FM-04Purge the stale entry file and chunks at the CDN and shorten their cache lifetime.
FM-05Pause further deploys until a change that invalidates cached frontend assets on deploy is in the release branch.
FM-06Decide between a rollback and a hotfix for the un-hashed or uninvalidated files, and record which asset URLs each option changes.
FM-07Tell affected users to hard refresh or clear the browser cache, and post the same steps on the status page.

Download the checklist

Pre-release checklist (Markdown)1.7 KB · v1.0.0
First 30 minutes checklist (Markdown)1.1 KB · v1.0.0

Only in this checklist

Every test class in this checklist also appears in at least one sibling checklist in the group; the item texts differ: Scan the build output and fail the release when any JavaScript file URL lacks a content hash in its file name.

Questions

What should be checked before a release to prevent Asset cache serves old bundle?

8 pre-release items, PR-01 to PR-08. PR-01: Scan the build output and fail the release when any JavaScript file URL lacks a content hash in its file name.

Is there a rollback plan for Asset cache serves old bundle?

The first-30-minutes checklist has 7 items. FM-01: Query frontend asset requests for 404 responses since the last deploy, because existing alerts may not cover them.

What should a team do in the first 30 minutes after Asset cache serves old bundle is detected?

The first-30-minutes checklist has 7 items. FM-01: Query frontend asset requests for 404 responses since the last deploy, because existing alerts may not cover them.

Which configuration checks apply to Asset cache serves old bundle?

PR-01: Scan the build output and fail the release when any JavaScript file URL lacks a content hash in its file name. PR-02: Confirm the remote entry file is served with a cache header that forces the browser to revalidate it on every load. PR-03: Confirm the previous deployment's hashed JavaScript assets still return 200 on the server after the new deployment goes live. PR-04: Confirm the deploy step purges every changed JavaScript chunk at the CDN and fails the deploy when the purge does not complete.

Is a Asset cache serves old bundle checklist still needed if deployment is automated?

Yes. Automation runs the steps; the checklist names what the tests must cover: configuration and environment tests, end-to-end tests and synthetic monitoring.

Which pipeline stages does the Asset cache serves old bundle checklist cover?

The pre-release items map to the pre-deploy and post-deploy stages.