If your app is packaged as a Docker container, AWS gives you three services that work together to run it: ECS to orchestrate containers, Fargate to run them without managing servers, and ECR to store the images.

ECS — Elastic Container Service

ECS launches Docker containers on AWS. The key thing about it: you provision and maintain the EC2 instances — the infrastructure — and AWS handles starting and stopping containers across those EC2s. It integrates with the Application Load Balancer.

        ECS Service
            │
       schedules
       containers
            │
   ┌────────┼────────┐
   ▼        ▼        ▼
  EC2      EC2      EC2
 (yours)  (yours)  (yours)

The split: you manage the EC2 instances; AWS manages placing and running containers on them.

Fargate

Fargate also launches Docker containers on AWS, but with one big difference: there is no EC2 to provision or manage. It is the serverless option — you specify the CPU and RAM your container needs, and AWS runs it.

       New Container
            │
            ▼
       ┌─────────┐
       │ Fargate │   (no EC2 visible)
       └─────────┘

The split: you manage nothing beyond the container and its CPU/RAM spec; AWS manages everything underneath.

ECR — Elastic Container Registry

ECR is a private Docker registry on AWS. It stores your Docker images, and ECS or Fargate pulls images from it to run them.

   ┌──────┐         ┌──────────┐
   │ ECR  │ ──pull──▶  Fargate  │
   │      │         │  / ECS    │
   │ Img1 │         │           │
   │ Img2 │         └──────────┘
   └──────┘

How the three fit together

You build Docker image
        │
        ▼
   push to ECR  ←── image storage
        │
        ▼
   ECS or Fargate pulls image
        │
        ▼
   container runs
   (on your EC2s = ECS,
    or AWS-managed = Fargate)

You build a Docker image, push it to ECR, and then ECS or Fargate pulls it and runs the container — on your own EC2s with ECS, or on AWS-managed infrastructure with Fargate.

Summary

  • ECS runs containers on your own EC2s — you own the infrastructure.
  • Fargate runs containers serverless — no EC2 to manage at all.
  • ECR is where your Docker images are stored.