Edge Caching for Web Services

Render provides edge caching for static assets (documents, images, etc.) served by paid web services. With edge caching enabled, you can speed up response times and reduce load on your web service:

Edge caching is powered by the same global CDN as Render static sites.

Setup

1. In the Render Dashboard, open your web service's Settings page and scroll down to the Edge Caching section:

   

2. Toggle the switch. A confirmation dialog appears.

3. Review the notices in the dialog, then click Confirm and enable.

You're all set! Render begins caching your web service's cache-eligible responses.

How edge caching works

Whenever a client sends an HTTP request to your cache-enabled web service, Render determines whether the request is eligible to serve from the edge cache. (For details, see Cache eligibility.)

If the request is cache-eligible, Render checks the edge cache for the corresponding resource.

• If the requested resource is in the cache (and the entry isn't stale), Render serves the cached version:

  

  In this case, the request never reaches your web service. This speeds up the response and reduces load.

• Otherwise, Render fetches the resource from your web service and—if it's also cache-eligible—caches it for future requests:

  

Cache eligibility

When serving a request from your web service, Render uses the following logic to determine whether the response can be cached for future requests:

^{* See details below.}

To summarize, all of the following must be true for a response to be cache-eligible:

• The originating request must use the GET or HEAD HTTP method.
• The requested resource must have a cache-eligible file extension.
• The response must either include a Cache-Control header that allows caching or have a default-cacheable status code.
• Additionally, the response must not include a Set-Cookie header.

Cache-eligible file extensions

A requested resource must have one of the following file extensions to be cache-eligible:

7z avi avif bin bmp bz2 class css csv dmg doc docx eot ejs eps exe flac gif gz ico iso jar jpeg jpg js mid midi mkv mp3 mp4 ogg otf pdf pict pls png ppt pptx ps rar svg svgz swf tar tif tiff ttf webm webp woff woff2 xls xlsx zip zst

Default-cacheable status codes

If your web service returns a cache-eligible response without a Cache-Control header, Render caches the response if it has one of the following status codes (and applies the corresponding default TTL):

Invalidation and expiration

To help ensure that clients receive up-to-date content, Render invalidates edge cache entries in the following scenarios:

Setting Cache-Control headers

You can customize Render's edge caching behavior for a particular resource by including a Cache-Control (or CDN-Cache-Control) header in your web service's response:

Cache-Control: public, max-age=7200

Cache-Control: public, max-age=3600

Cache-Control: no-cache

Cache-Control: stale-while-revalidate=60, stale-if-error=3600, public, max-age=1200

Precedence rules

Render applies the following precedence rules to cache control headers:

• The CDN-Cache-Control header takes precedence over the Cache-Control header if both are present.
• The s-maxage directive takes precedence over the max-age directive if both are present.

Inspecting cache behavior

Each response from a cache-enabled web service includes a CF-Cache-Status header:

CF-Cache-Status: HIT

The value of this header indicates whether the response interacted with the edge cache and in what way. The most common values are: