The AWS Cloudfront Fix-It Series
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A troubleshooting field guide for Amazon CloudFront
AWS CloudFront is not a black box; it is a layered system of edges, caches, and origins. When it fails, it leaves specific signals—but you have to know where to look.
This series moves beyond "try invalidating it" and provides a methodical approach to diagnosing and fixing the most common CloudFront failures.
The Lineup
Fix-It #1: 403, 404, and 502 — What CloudFront Is Really Telling You
Decodes the three primary infrastructure signals to tell you exactly which layer (Edge, Origin, or Trust) is rejecting your request.
Fix-It #2: “Why Didn’t My Change Apply?” — Caching, TTLs, and Propagation Reality
Explains why valid configuration changes remain invisible, distinguishing between Edge caching, Browser caching, and the role of invalidations.
Fix-It #3: TLS, ACM, and Certificate Mismatch Failures
Solves the "us-east-1" requirement, CNAME circular dependencies, and the 502 Bad Gateway errors caused by origin handshake failures.
Fix-It #4: Performance & Latency Failures (Why Is My Site Slow?)
Debugs high latency by isolating Cache Misses, Price Class limitations, and Origin bottlenecks using the X-Cache header.
Fix-It #5: Headers That Disappear, Reappear, or Mutate at the Edge
Fixes missing headers and CORS errors by aligning Origin Request Policies (what the backend sees) with Cache Keys (how the edge splits content).
Fix-It #6: Debugging CloudFront When You Can’t SSH Into Anything
A methodology for diagnosing a system with no shell access, using Request IDs (X-Amz-Cf-Id), delayed logs, and Athena to prove where the failure lies.
The Philosophy
- Stop Guessing: Treat errors as signals, not bugs.
- Stop Invalidating: Fix the root cause first.
- Start Segmenting: Isolate the Edge from the Origin.
Predictable infrastructure is the goal.
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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