Building a Portable FastAPI Backend for AWS Lambda and ECS Using Terraform
In the previous post, we explored how to deploy a FastAPI application on AWS Lambda using an ASGI adapter. This is a great option for early-stage projects: it requires zero infrastructure management, supports rapid iteration, and scales automatically.
But as your application matures, Lambda’s trade-offs can become limiting:
- Cost scaling with consistent traffic
- Compute/memory coupling and lack of vertical scaling
- Package size limits and cold starts
That’s why many teams adopt a container-based workflow that can run on both Lambda (via container images) and ECS Fargate. With a little planning, you can build once and deploy to either platform with minimal friction.