Keep-Alive connection issue when CF Proxy is enabled

We're using Orange Cloud (proxy mode enabled) for our application. When sending multiple requests in a short time, we frequently get timed-out requests when the Cloudflare proxy is ON.
We noticed that Keep-Alive connections drop to 0 when the Cloudflare proxy is active. Our backend server (NGINX) has Keep-Alive properly configured and enabled, and when we bypass Cloudflare (grey cloud/direct to origin), Keep-Alive works normally and we have no timeout issues.
Can anyone help explain why Cloudflare appears to disable or override Keep-Alive connections to the origin, and how we can configure or increase the Keep-Alive limit (or enable persistent connections) when proxying through Cloudflare?

SuperHelpflare•12/1/25, 9:47 AM

Support AI

According to the documentation, Cloudflare maintains keep-alive connections to improve performance and reduce the cost of recurring TCP connects in the request transaction as Cloudflare proxies customer traffic from its global network to the site's origin server. However, it's also mentioned that origin web servers close TCP connections if too many are open.

It's possible that the issue you're experiencing is related to the

Proxy Idle Timeout

Proxy Idle Timeout

limit, which is set to 900 seconds (15 minutes) by default. This means that Cloudflare will reuse open TCP connections up to this limit after the last HTTP request.

To configure or increase the Keep-Alive limit, you can refer to the documentation on Configurable limits. However, it's noted that some TCP connections can be customized for Enterprise customers, so you may need to reach out to your account team for more details.

Additionally, you can also check the HTTP keep-alive (persistent HTTP connection) section, which mentions that Cloudflare reuses open TCP connections for up to 15 minutes (900 seconds) after the last HTTP request.

It's also worth noting that the documentation mentions that Session cookies can be used to track and bind user sessions to a specific server, and that configuring the load balancer to parse HTTP requests by cookie headers can help avoid issues with keep-alive connections.

Source: https://developers.cloudflare.com/fundamentals/reference/connection-limits/, https://developers.cloudflare.com/load-balancing/load-balancers/

Sources

This is an AI generated response, it may not be 100% accurate. Please validate the output. You can ask followups by replying to this message or mentioning me.

sampahSarap•12/8/25, 3:06 PM

Disable dont think soo, try look at the connection limit devdocs
https://developers.cloudflare.com/fundamentals/reference/connection-limits/

Cloudflare Docs

Connection limits

When HTTP/HTTPS traffic is proxied through Cloudflare, there are often two established TCP connections: the first is between the requesting client to Cloudflare and the second is between Cloudflare and the origin server. Each connection has their own set of TCP and HTTP limits, which are documented below.

Keep-Alive connection issue when CF Proxy is enabled

Similar Threads

Similar Threads

Similar Threads