Troubleshooting 404 Responses: Connecting a Next.js Frontend with a Node.js API on AWS ECS Fargate

Frontend and Backend Development
1

I deployed Dockerized Next.js front end with Node.js API on AWS ECS Fargate. An ALB directs front end traffic, but API calls return 404 errors. Example:

{
  "clusterName": "demo-group",
  "serviceList": [
    { "serviceId": "client-web", "portNumber": 4000 },
    { "serviceId": "backend-api", "portNumber": 8000 }
  ]
}
2

hey, check ur backend’s routes configuration - had a simlar issue cause of wrong alb target group rules mapping. small misconfig in port routing did the trick for me.

3

hey, have u chcked if the container’s exposed ports match the alb listener? i haz seen this hiccup when node setup and network congif misauth. any extra log info to clue us in?

4

In my experience, resolving such issues often involves a careful review of both the ECS task definition and ALB configuration settings. I discovered that updating the task’s port mapping and verifying that the ALB listener rules targeted the correct container ports was crucial. Ensuring that the API endpoint paths are correctly defined in the Node.js routes and matching the ALB rules also helped. It is essential to inspect container logs and monitor network flows to isolate whether the error results from configuration mismatches in the service definitions or routing details.