Where it genuinely helps
- Static assets served from a nearby edge — images, CSS, JavaScript, fonts.
- TLS termination close to the visitor, which removes a round trip on a slow network.
- Absorbing traffic spikes and abusive load before they reach the origin.
- HTTP/2 and HTTP/3 without touching the origin server's configuration.
- Full page caching at the edge — but only for pages you have deliberately made cacheable.
Where it hides the problem
The dangerous case is a site that looks fast to its owner because their pages are cached at the edge, while every logged-in visitor, every cart, every checkout and every search result bypasses the cache entirely and meets the original slow origin. The store's best pages are fast; its buying pages are not. The report says the site improved.
Where it creates new problems
| Setting | What it breaks |
|---|---|
| Caching HTML without excluding cart and checkout | One customer sees another customer's cart |
| Rocket Loader / automatic JS deferral | Theme and plugin scripts that expect document order |
| Aggressive minification of inline JS | Anything that was already minified or templated |
| Bot Fight Mode | AI crawlers, uptime monitors and legitimate integrations |
| Auto-minify on an RTL stylesheet | Nothing, usually — but it is the first thing blamed |
The order to do this in
- Measure time to first byte at the origin, with the CDN bypassed.
- Fix the origin: queries, object cache, PHP version, hosting that is not oversold.
- Make the pages that can be cached actually cacheable, and exclude the ones that cannot.
- Then add the edge, and re-measure the same four page types.
- Verify that a non-browser client still receives a 200.
Sources
Related services
Related work
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