Deploying a Spring Boot Microservice on AWS Fargate: Lessons From the Outage That Forced Me to Get It Right

My first attempt to deploy a Spring Boot microservice on AWS Fargate didn’t fail loudly. It failed quietly — in a loop. ECS kept launching tasks, the Application Load Balancer kept marking them unhealthy, and the service never stabilized. The logs looked fine, the container looked fine, but the ALB replaced every task within seconds.

The root cause was painfully simple: Spring Boot needed 45 seconds to start, and my ALB health‑check timeout was 5 seconds. The tasks never had a chance.