What is the name of the domain?
there are multiple domains affected
What is the issue you’re encountering
Intermittent Delays with Cloudflare Proxy ON – Origin Server Responds Slowly Only on One Server
What steps have you taken to resolve the issue?
Hi all,
We have two almost identical Plesk servers. We’re experiencing a frustrating issue on one of them (server01) where page loads are intermittently delayed by up to 10 seconds, but only when Cloudflare proxy is enabled. When we disable proxy mode (grey cloud), the issue disappears entirely. I am also in conversation with my host (both servers are fully managed) to see if they can shed any light on the issue from their end.
Setup Summary
Both server01 (problematic) and server02 (working fine) are Plesk servers running mostly Apache with FastCGI for PHP (have tested php-fpm too, no difference). Both servers are not under load stress and have plenty of resources available. In fact, server02 which is fine has over 200 domains and server01 only has 50.
Both use the same Cloudflare DNS and proxy configuration, under the same account and nameservers.
The issue affects both front-end and wp-admin performance, but only on server01.
Proxy mode OFF → Fast performance
Proxy mode ON → Random 5–10s delays to load pages (intermittent)
No load issues on server01 — it’s actually lower-traffic than server02.
SSL/TLS setup is Cloudflare Universal SSL (edge certificates), identical on both.
What We’ve Tested:
SSL Labs – No differences in TLS or cipher configurations. Identical A-grade scores across all IPv4/IPv6 nodes.
Server01 vs Server02 Response Times
Fast and consistent on server02, even with higher traffic.
Intermittent delays only occur on server01 when proxied.
Keepalive / cold connection theory – Initially thought low traffic on server01 might cause Cloudflare to repeatedly open new connections, but issue persists even after several “warm” clicks.
No custom WAF, rules, or rate-limiting on Cloudflare.
Origin server is responsive when tested directly (without CF).
Have also tested proxying via a different CF account that has different name servers. Same issue.
Suspected Causes:
Network latency or DNS resolution delay between Cloudflare PoPs and the server01 IP?
Possible de-prioritisation or connection issue specific to that IP block?
We’d love suggestions on how we can resolve this, as we want to proxy traffic for server01 sites.
How we can test Cloudflare edge-to-origin latency or confirm if CF is having difficulty connecting to the origin server.
If there’s any known behaviour where low-traffic origin servers struggle to maintain optimal connection with Cloudflare on the free plan.
Suggestions to help reduce Cloudflare-origin connection delay in this kind of setup.
Any insights or advanced debugging suggestions would be massively appreciated!
Thanks in advance,
James
What are the steps to reproduce the issue?
We reproduce the issue by visiting the front-end and back-end of sites running on server01 vs server02, both proxied and not proxied via cloudflare