A 502, commonly called a bad gateway error, means a server acting as a middleman, a reverse proxy, a load balancer, a CDN edge node, sent the request onward and got back an invalid or unusable response from the server behind it. The problem isn't the gateway itself; it's whatever it's trying to talk to.
This tends to show up during deploys, when a backend server restarts mid-request, during traffic spikes that overwhelm an origin server faster than the gateway expects, or when a misconfigured proxy points at the wrong upstream address entirely. It usually resolves itself once the backend server recovers, but if 502s show up repeatedly rather than as a one-off blip, that's a sign the infrastructure behind the gateway needs attention rather than the gateway configuration itself. For SEO, the same crawl-frequency risk applies as with any recurring server error: a search engine that keeps hitting 502s on a site will slow down how often it comes back to check.
