Between 11.7 and today, there has been a spike in the CPU time required to render a page in our users’ browsers.
This seems to be blocked by the new CSS. We haven’t made any adjustments on our side, but we do make regular updates (almost daily).
Here is some data to get a better idea of the problem. On the left is 11.7
But the problem may be elsewhere, as there have been a lot of updates to Docker recently, for self-hosted Discourse.
Anyone else have the same problem?
Do you know what version of Discourse was on 11.7 and which one started to show issues?
Unfortunately I’m not able to say, we don’t keep such detailed logs with the Discourse community.
But from the log I managed to dig out this <meta name="generator" content="Discourse 3.3.0.beta4-dev - https://github.com/discourse/discourse version 39187d98149e9822a8c9c21da9c1dc6a7aff4e49">
This would be the last state where it still worked OK.
That’s supposed to be “<meta name="generator" content="Discourse 3.3.0.beta4-dev - https://github.com/discourse/discourse version 39187d98149e9822a8c9c21da9c1dc6a7aff4e49">”, pulled from raw post contents for anyone who needs it.
How are these metrics being collected?
In your screenshot of LCP measurements, the “previous” screenshot seems to show the basic-html crawler view, while the “current” screenshot shows the full JS app which is presented to users.
It makes sense that the full JS app has higher CPU time and page weight.
So I think this is likely a change in the monitoring system, or perhaps the way in which Discourse responds to your monitoring system. 
All images are from a single system that measures consistently the same. Only the measurements were taken on different days. So the conditions on the Discourse side have probably changed.
For more information on how DebugBear measures, see here. A Guide to Website Monitoring | DebugBear
