How to Fix Nginx 502 Bad Gateway on AWS ALB / CloudFront Upstream Connection
Nginx returns 502 errors specifically when deployed behind AWS Application Load Balancer or CloudFront, even though the same Nginx configuration works fine...
Blog
All troubleshooting articles, newest first.
How to Fix Nginx Proxying to Next.js App Router Returning Static Assets 404
Your Next.js app works fine in local development, but once deployed behind Nginx, CSS, JS chunks, and other static assets return 404 while the actual pages...
How to Fix Nginx SSL Certificate net::ERR_CERT_COMMON_NAME_INVALID After Certbot Run
The browser rejects your site's certificate with a common name mismatch error, even though you just ran Certbot and it reported success. This means the...
How to Fix Nginx Rate Limiting Throwing 503 Instead of 429 to End Users
You've set up Nginx's rate limiting to protect an endpoint from abuse, and it's working — but rate-limited clients see a 503 Service Unavailable instead of the...
How to Fix Nginx WebSockets "Connection: Upgrade" Header Dropped Behind Load Balancer
WebSocket connections work fine when testing directly against Nginx, but fail once a load balancer (ALB, ELB, or another reverse proxy) sits in front of it....
How to Fix MySQL "Gtid_set Has Holes" Error on Replication Slave Setup
Setting up or resuming GTID-based replication fails with MySQL complaining about "holes" in the GTID set, refusing to proceed. This is MySQL's GTID consistency...
How to Fix MySQL Connection Pool Timeout on AWS RDS Proxy Idle Instances
Your application's first request after a period of low traffic fails with a connection timeout when going through RDS Proxy, even though the underlying RDS...
How to Fix MySQL "Out of Memory" Crash During Large ALTER TABLE Migration
Running an ALTER TABLE on a large table crashes the MySQL server outright with an out-of-memory error, rather than just running slowly. Certain schema changes...
How to Fix MySQL JSON_EXTRACT Query Not Using Functional Index in MySQL 8
You've created a functional index specifically to speed up queries filtering on a value inside a JSON column, but EXPLAIN shows MySQL is still doing a full...