ECS, Fargate & ECR Overview

🧠 Core Idea

Containers can't run on their own — they need a platform to launch and manage them. AWS gives you three services for that:

• Amazon ECS — runs containers on EC2 instances you manage

• AWS Fargate — runs containers with no servers to manage

• Amazon ECR — stores the Docker images ECS/Fargate deploy

Knowing how these three fit together is a key exam concept.

📦 Amazon ECS (Elastic Container Service)

ECS is AWS's managed container orchestration service — it deploys and runs your Docker containers.

AWS handles the container lifecycle (start, stop, monitor, schedule), but you provide the compute: you launch and maintain the EC2 instances that host the containers.

Think of ECS as deciding:

• Which container runs, and where

• When it starts or stops

• How work spreads across your EC2 instances

It also pairs well with an Application Load Balancer for scalable web apps.

💡How it works:

1. Launch EC2 instances

2. ECS agent installs automatically (ECS-optimized AMIs)

3. Register instances with an ECS cluster

4. Store your Docker image in a registry

5. Create an ECS task

6. ECS places the container on an available instance

7. ECS monitors and manages it

🚀 AWS Fargate

Fargate also runs Docker containers — but you never create or manage EC2 instances. AWS handles the infrastructure behind the scenes.

You just specify:

• The Docker image

• CPU needs

• Memory needs

AWS launches the container automatically. No servers to provision = serverless container service.

💡How it works:

1. Store your Docker image

2. Specify CPU/memory

3. Deploy the container

4. AWS provisions infrastructure automatically

5. Container runs — no EC2 management involved

⚖️ ECS vs. Fargate

Both run Docker containers on AWS — the real difference is who manages the servers.

🗂️ Amazon ECR (Elastic Container Registry)

Before ECS or Fargate can run a container, they need an image to pull from. Amazon ECR is AWS's private Docker image repository — a secure place to store images before deployment.

💡How it works:

1. Build a Docker image

2. Push it to ECR

3. ECS or Fargate pulls the image from ECR

4. AWS runs a container from it

🔗 How They Work Together

• ECR stores your Docker images

• ECS or Fargate retrieves those images

• The image becomes a running container

• Your app goes live

Docker Image → Amazon ECR → Amazon ECS or AWS Fargate → Running Container

🎓 Exam Tips

• ECS = containers on EC2 you manage

• Fargate = containers, serverless

• ECR = private Docker image storage

• Both ECS and Fargate can deploy images stored in ECR

• "Where are Docker images stored on AWS?" → ECR

• "Serverless way to run containers?" → Fargate

🧠 Key Takeaways