We had 30-40 min site slowdowns 2h ago and servers were totally ok (no overload or any problem).
It seems problems came from Cloudflare.
Any information about a possible problem ?
You can always check https://cloudflarestatus.com to see if there are any ongoing (or past) issues, which seems to match with the timestamps of when you saw problems.
What exactly are you basing this on?
If your own ISP had some congestion issues within their network, causing slowdowns, which actually seems quite common with several ISP’s during e.g. peak hours, then you are not looking to dig in to it with Cloudflare, but with your own ISP.
Cloudflare mentions what are issues with Cloudflare’s own network on the above page, but not what are issues with third parties (such as e.g. your own ISP), which would be up to them (your own ISP) to provide information about.
The servers behind slow sites are doubled monitored (for hardawre and network).
There was no problem at this level.
The main problem was website’s images was displayed very slowly.
And the only cache for images is the Cloudflare one …