AWS CloudFront Error: “Why Didn’t My Change Apply?” — Caching, TTLs, and Propagation Reality
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How CloudFront changes work correctly at the origin but fail to appear at the edge due to cached responses, TTL precedence, cache key configuration, and browser-level caching
Problem
Configuration changes made to Amazon CloudFront appear to have no effect. Updated content, headers, permissions, or behaviors do not reflect in responses, even after deployments complete successfully.
Clarifying the Issue
CloudFront is a cache-first system.
Once content or metadata is cached at the edge, CloudFront will continue serving it until the cache entry expires or is explicitly invalidated, regardless of changes at the origin.
This is not a delay, a bug, or a failed deployment.
It is CloudFront doing exactly what it was designed to do.
Most “changes not applying” issues are caused by cached responses outliving the configuration change that was meant to affect them.
Why It Matters
Caching amplifies mistakes:
- Incorrect headers persist
- Broken paths keep failing
- Fixed permissions appear ignored
- Debugging becomes guesswork
Without understanding cache behavior, engineers often redeploy, invalidate blindly, or change IAM and origin settings unnecessarily.
Key Terms
- TTL (Time to Live) – How long CloudFront keeps an object in cache (Min, Max, Default)
- Edge Cache – Cached responses stored at CloudFront locations globally
- Browser Cache – Cached responses stored locally on the user’s device (outside CloudFront’s control)
- Origin Headers – Directives (such as
Cache-Control) sent by the backend that instruct CloudFront how to cache - Invalidation – A manual request to forcibly remove cached objects from the edge
- Cache Key – The specific combination of request attributes (URL, headers, cookies, query strings) CloudFront uses to identify a unique object
Steps at a Glance
- Identify what was changed
- Determine where the data is cached (Edge vs Browser)
- Check TTL and behavior settings
- Confirm the Cache Key configuration
- Invalidate or wait, intentionally
Detailed Steps
Step 1: Identify What You Changed
Cached changes include:
- Object content (HTML, CSS, JS, images, JSON)
- Response headers
- Error responses (4xx / 5xx)
- Redirects
Non-cached changes include:
- Distribution settings (after deployment completes)
- TLS certificates
- Origin connection settings
If the change affects response content or headers, caching is almost always involved.
Step 2: Determine Which Cache Is Involved
There are two primary places stale data lives:
- CloudFront Edge Cache – The global CDN is serving an older object
- Browser Cache – The user’s local browser has cached the file
Critical check:
If you invalidate CloudFront and still see old content, open browser DevTools.
If the response shows disk cache or memory cache, CloudFront is not the problem.
Step 3: Check TTL Configuration
CloudFront determines caching behavior using a precedence hierarchy:
- Origin
Cache-Controlheaders (within Min/Max TTL bounds) - CloudFront Default TTL (when no origin header exists)
- CloudFront Min / Max TTL (hard limits)
Common mistakes:
- Origin sends
Cache-Control: max-age=31536000, locking files in browsers - Default TTL set to hours or days, masking fixes
- Assuming a deployment clears cached objects (it does not)
Step 4: Verify the Cache Key
CloudFront only differentiates objects using attributes in the Cache Key.
If content varies by a request attribute not included in the Cache Key:
- CloudFront ignores that attribute
- The first response cached is reused incorrectly
Example:
- App varies by
Accept-Language - Header not included in Cache Key
- One language response is served to all users
Action:
Ensure every header, cookie, or query string that affects content is explicitly included in the Cache Key policy.
Step 5: Invalidate or Wait — Deliberately
Invalidations are a tool, not a fix.
Use invalidations when:
- The root cause is already fixed
- Immediate consistency is required
Do not invalidate to “see if it works.”
That hides configuration errors and increases cost.
Pro Tips
- Prefer versioning over invalidation:
app.v2.jsbeatsapp.jsevery time - Rule out local cache first: Test with
curlor disable cache in browser DevTools - Error responses are cached: 403 and 404 responses respect Error Caching TTLs
- Fix first, invalidate second
Conclusion
When CloudFront changes don’t appear to apply, the system is usually behaving correctly.
The cause is almost always one of the following:
- Browser Cache holding stale content locally
- Edge Cache honoring a longer-than-expected TTL
- Cache Keys excluding the attribute that changed
Once you check the browser and the cache key, CloudFront becomes predictable.
Aaron Rose is a software engineer and technology writer at tech-reader.blog and the author of Think Like a Genius.
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