Improving Netlify's CDN performance

Hi,
While benchmarking different CDN providers, I’ve noticed that Netlify has a suboptimal use of the Date header.

Consequences

  • Clients (visitors of Netlify’s sites, browsers) miss their local cache
  • Thus it increase the requests to Netlify’s edge servers which result in an increase in bandwidth usage, which has a cost
  • It also result in a increase in the TTFB, especially for resources like .js .css .jpg because even when a resource should be fetched from browser’s cache, it result in a network request.

Problem

Netlify set the Date HTTP header to the date when the CDN server cached the resource, instead of the time the request is server.
Due to that, Browsers are misusing their local cache, which increase TTFB and bandwidth usage.
You can read here the detailed math: https://forums.aws.amazon.com/thread.jspa?messageID=807813

Solution

Edge servers must set the Date Header to the time the request was served.
They can use the last-modified header to indicate when the file was modified.

It will result in improved local (browsers) cache hit by all visitors, which will reduce bandwidth usage, TTFB and costs.

Examples in the wild

Both Firebase hosting and StackPath are setting the Date header to the time the request is served, and the last-modified header to the time the site is deployed.

Hey @skerkour,
Many thanks for this report! This has been filed as a bug internally. We’ll share updates in this thread or over at --> Http server clock as we get them.

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