Only some pages return 502

Updated on October 20, 2026 by Nurbol Sakenov

The homepage loads. Checkout, or one API route, shows 502 Bad Gateway. The name resolved, the port opened, and the certificate was accepted. Compare two URLs before you restart anything.

1. Curl the URL that works and the URL that fails

Run both from the machine where you are debugging. Use the path customers actually opened.

curl -sI --max-time 20 https://example.com/
curl -sI --max-time 20 https://example.com/checkout

The first command is the page that still loads. The second is the one that fails in the browser.

Read both status lines before you open a process manager or change DNS.

Either command exits before a status line. Connection refused, timeout, or a certificate error means the problem is below HTTP for that request. Walk the name, the port, and the certificate in DNS works, the site does not.
Both status lines are 502. Every path you tried failed the same way from here. That is a whole-host failure from this client, not “one path only.” Use the same DNS post.
The homepage is 200 and the other URL is 502. DNS, the port, and TLS worked for this host. The proxy in front answered on both requests. Only the backend for that path failed. Section 2 is where you stop.
The other URL is 404. The server answered and said the path is missing. That is not a bad gateway. A missing page can still count as up on a Website check; see When 403 means up.
Both status lines are 200, and the browser still shows 502. curl sent no cookies or session. The failure is tied to what the browser sends. Reproduce with the same cookies before you restart the app.

A 301 or 302 is a redirect, not a 502. Follow it with curl -sI -L --max-redirs 8, or run curl on the final URL, then read that status line. If a URL appears twice in the chain, stop in Too many redirects.

2. Read the 502 response

On the 502 response, the Server header names the proxy that gave up: Cloudflare, nginx, a load balancer. 502 means that proxy did not get a valid response from the process behind this path.

The homepage 200 means that proxy is running. Restarting the proxy does not start the upstream that only this route uses. Look at the app process, the timeout, or the route rule that sends this path to a different backend.

504 is the sibling failure: the proxy waited and gave up on a slow upstream. The homepage still shows the proxy itself is up. If only one path is 504, compare those two URLs in Only some pages return 504.

3. Monitor the path that failed

A check on / can stay green while /checkout returns 502. Add a Website or API check on the URL that returned 502. 502 is down for Website and API checks. Status-code rules are in When 403 means up; the form is Add a check.

Leave the confirmation period at three failures. One 502 is stored. It does not open an incident.

Validation report

Validation summary

Status validated

Date: 2026-10-20

Host: scaledpapers.com

What was checked

The post opens with two curl -sI commands: one URL that loads, one that does not. These runs use the homepage, a blog article, and a path that does not exist on this host.

1. Homepage and a blog path

curl -sI --max-time 20 https://scaledpapers.com/
HTTP/2 200
server: cloudflare

curl -sI --max-time 20 https://scaledpapers.com/blog/too-many-redirects/
HTTP/2 200
server: cloudflare

Both status lines are HTTP/2 200. Cloudflare answered for each URL.

2. Path that does not exist

curl -sI --max-time 20 https://scaledpapers.com/no-such-path-502-check
HTTP/2 404
server: cloudflare

The status line is HTTP/2 404. The post treats that as a missing page, not a bad gateway.

Branch: homepage and blog path are 200; the missing path is 404. No URL returned 502.