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CloudFlare CDN and TTFB (Time To First Byte)

Often clients teset their page load speeds, eg with a site like http://www.webpagetest.org/ ,  and see something like this in the results:

 

cdn-pagespeed-failed

 

They see the "F" result and get very concerned that their page load is slow.

Don't worry about this in the least!

It is simply the way this particular test works, and is by no means a failure.   

"Time To First Byte" is often used as a measure of how quickly a web server responds to a request and common web testing services report it. The faster it is the better the web server (in theory). But the theory isn't very good.

From the end user perspective TTFB is almost useless. In this (real) example it's actually negatively correlated with the download time: the worse the TTFB the better the download time.

Probably the only time TTFB is useful is as a trend. And it's best measured at the server itself so that network latency is eliminated. By examining a trend it's possible to spot whether there's a problem on the web server (such as it becoming overloaded).

Measuring TTFB remotely means you're also measuring the network latency at the same time which obscures the thing TTFB is actually measuring: how fast the web server is able to respond to a request.

 

Here is an article from CloudFlare on this.....  WARNING....   it;s more than a a little technical! http://blog.cloudflare.com/ttfb-time-to-first-byte-considered-meaningles/