CORS for Multi-Region API Deployments
Multi-region APIs are great right up until the browser gets involved. Your backend can happily serve traffic from us-east-1, eu-west-1, and ap-southeast-1, but once a frontend starts calling those endpoints cross-origin, CORS becomes one of the easiest ways to break an otherwise solid deployment. I’ve seen teams spend days debugging “random” browser failures that turned out to be region-specific CORS drift. If you run APIs behind a CDN, global load balancer, edge worker, or region-aware gateway, you need to treat CORS as part of your routing architecture, not just a couple of headers added somewhere in Express. ...