How to Choose Cache Tools

Cache incidents are solved faster when split into three paths: no caching, failed revalidation, and layer mismatch.

First tool by symptom

Update not reflected → Cache Not Working Troubleshooting
Always 200 instead of 304 → Cache Diagnostic
Only CDN path is stale/different → HTTP Cache Mismatch

Tool role map

Cache Not Working Troubleshooting: symptom-first entry point
Cache Response Analyzer: decision from a single response
HTTP Cache Mismatch: compare behavior across environments
Cache Diagnostic: cross-header comprehensive diagnosis
Cache Control Overview / Inspect: policy design and directive-level details

Recommended practical flow

1) Fix the symptom and choose the first entry tool
2) Collect header evidence using Response Analyzer or Diagnostic
3) If CDN behavior differs, move to Mismatch and isolate delivery layers
4) Finalize cache policy with Overview/Inspect to prevent recurrence

Headers to always collect

Response: Cache-Control, ETag, Last-Modified, Expires, Age, Vary
Request: If-None-Match, If-Modified-Since, Cache-Control
Path info: Via, X-Cache, and CDN-identifying response headers
Collect from browser, CDN, and origin for the same URL

Policy by resource type

HTML: short TTL + revalidation (no-cache or short max-age)
API (JSON): no-store for sensitive data, validators for public data
Static assets: versioned URL + long max-age + immutable
CDN: separate s-maxage policy from browser-facing directives

Compared tools

Common mistakes

Applying immutable to HTML and delaying deployment reflection
Emitting validators without checking inbound If-* requests
Comparing browser and CDN outcomes as if they were the same layer

Post-fix recheck points

Verify expected first 200 then revalidation 304 sequence
Confirm old HTML does not remain stale after deploy
Confirm Age resets as expected after CDN purge
Check that cache branch count does not explode after Vary changes

Incident runbook

Identify failing layer first (browser/CDN/origin)
For mitigation, temporarily shorten HTML TTL to reduce impact
Apply durable fixes with URL versioning and validator alignment
Prevent recurrence with recurring header-diff monitoring

FAQ

What if I cannot choose the first tool?: Start with Troubleshooting for stale updates, Diagnostic for missing 304, and Mismatch for layer differences.
What is the difference between Cache-Control Inspect and Overview?: Inspect focuses on per-response interpretation, while Overview is for policy design and directive planning.

Referenced specs

Next to view (diagnostic order)

These links are generated from site_map rules in recommended diagnostic order.

Cache Not Working Troubleshooting — Troubleshoot cache-not-working symptoms step by step from headers
HTTP Cache Mismatch — Identify root causes of cache mismatches
Cache Response Analyzer — Judge cacheability from response headers
Cache Diagnostic — Run cross-header diagnostics for HTTP caching
Cache Control Overview — Summarize how to use Cache-Control/Pragma/Expires together
Cache-Control Inspect — Parse and interpret Cache-Control directives