Every IAM error, every Docker rate limit, every Testcontainers gotcha documented. The guide I wish existed when I started. Most AWS deployment guides show you the happy path. This one shows you the whole road — including the potholes. This is the complete walkthrough for deploying a Spring Boot app to AWS ECS with a real CI/CD pipeline. GitHub Actions for testing. CodePipeline + CodeBuild for deployment. Every IAM permission. Every command. Every error documented. What You're Building GitHub PR → GitHub Actions → tests pass → PR shows ✅ GitHub push to main → CodePipeline → CodeBuild (test + build JAR + build Docker image + push to ECR) → ECS rolling deploy (zero downtime) → SNS email notification Stack: Spring Boot 4.0.5 / Java 21 / Maven MySQL 8 on Amazon RDS Docker → Amazon ECR Amazon ECS GitHub Actions + AWS CodePipeline + CodeBuild Step 1 — RDS MySQL Create a db.t3.micro instance (free tier eligible): Engine : MySQL 8.0 Template : Free tier Public access : Yes (dev only — lock this down in production)…