Q: What causes a 502 Bad Gateway and how should I start diagnosing it? A: A 502 Bad Gateway occurs when a gateway server like a CDN or reverse proxy cannot get a good response from your application. Common triggers include traffic spikes, bad deploys, service crashes, DNS or SSL issues, and upstream timeouts that are too short. To begin learning how to fix 502 bad gateway, confirm the problem and rule out the browser before moving inward to edge and origin checks. Q: How do I confirm a 502 is not caused by the user’s browser or network? A: Refresh the page, try another browser or an incognito window, clear cache and cookies, and test on a second device or mobile data to rule out local DNS or caching issues. Use down detectors or your status page to see if others report the problem, which is the first step in how to fix 502 bad gateway. Q: What checks should I perform at the CDN or WAF when I see a 502? A: Review the provider status and enable failover or bypass cache if they report an outage, and pause the proxy to hit the origin directly to isolate the edge. Check WAF rules and rate limits (whitelist needed routes or disable a new rule), and confirm the CDN can reach your origin IP and port to help how to fix 502 bad gateway quickly. Q: What reverse proxy or load balancer issues commonly cause 502s and what quick fixes help? A: Read proxy error logs for messages like “upstream timed out,” “bad gateway,” or “connection refused” and ensure backends are healthy and listening on the correct sockets or ports. Temporarily raise timeouts (for example proxy_read_timeout or fastcgi_read_timeout), check worker limits and connection pools, and validate config (for example nginx -t) before safely reloading as part of how to fix 502 bad gateway. Q: What immediate fixes can restore my site in minutes during a 502 outage? A: Follow the restart order cache → app → proxy to clear dead connections, briefly raise timeouts to ride out spikes, or roll back the last deploy if errors began after a release. You can also scale out app instances or workers, purge or bypass CDN cache, or disable a new WAF rule to quickly implement how to fix 502 bad gateway. Q: Which commands and logs are most useful for troubleshooting a 502 from my laptop or server? A: From your laptop use curl -I and curl -v to check status, TLS, and upstream errors and use dig to inspect DNS records. On the server tail proxy logs, use journalctl for app services, ss -ltnp to check listening ports, and tools like top, free, and df to inspect resource issues while you follow steps on how to fix 502 bad gateway. Q: How can I prevent future 502 incidents and improve resilience? A: Set reasonable timeouts, use health checks to remove bad backends quickly, return 429 for rate limits instead of 502, and use connection pooling to avoid thundering herds. Add autoscaling and caching for expensive queries, adopt canary or blue-green deploys and versioned config, and strengthen observability and alerts to reduce repeats and speed up how to fix 502 bad gateway. Q: What restore plan should my on-call team follow to restore service fast during peak hours? A: Verify the outage and note start time and scope, check CDN/WAF dashboards and bypass the edge to hit the origin if needed, then read proxy and app logs for upstream timeouts or crashes. If errors started after a release raise timeouts and restart app workers in order, roll back the deploy if required, scale workers if CPU or connections are maxed, then tune timeouts back and document the fix as part of how to fix 502 bad gateway.