ECS EC2 vs ECS Fargate: Key Differences and When to Use Each

AWS ECS EC2 lets you run containers on your own EC2 instances, giving you control over the servers. ECS Fargate runs containers without managing servers, handling infrastructure automatically for you.

Quick Comparison

Here is a quick side-by-side comparison of ECS EC2 and ECS Fargate based on key factors.

Factor	ECS EC2	ECS Fargate
Infrastructure Management	You manage EC2 instances	AWS manages infrastructure
Scaling	Manual or auto scaling of EC2 instances	Automatic scaling per task
Cost Model	Pay for EC2 instances regardless of usage	Pay per running task resources
Control	Full control over instance OS and config	Limited control, serverless model
Setup Complexity	More setup and maintenance	Simpler, no server setup
Use Case	When you need custom OS or software	When you want easy, serverless containers

Key Differences

ECS EC2 requires you to launch and manage Amazon EC2 instances as the underlying servers for your containers. You decide the instance types, sizes, and scaling policies. This gives you full control over the operating system, installed software, and network settings. However, you must handle patching, capacity planning, and instance health.

In contrast, ECS Fargate is a serverless compute engine that runs containers without you managing servers. You only specify the CPU and memory for each task, and AWS automatically provisions and scales the infrastructure. This reduces operational overhead and simplifies deployment but limits your control over the environment.

Cost-wise, ECS EC2 charges you for the EC2 instances whether your containers fully use them or not, which can lead to inefficiencies. ECS Fargate charges based on the exact CPU and memory resources your containers consume, often making it more cost-effective for variable workloads.

Code Comparison

Here is an example of an ECS task definition snippet for running a simple container on ECS EC2.

json

{
  "family": "ec2-task",
  "containerDefinitions": [
    {
      "name": "web",
      "image": "nginx",
      "memory": 512,
      "cpu": 256,
      "essential": true,
      "portMappings": [
        {
          "containerPort": 80,
          "hostPort": 80
        }
      ]
    }
  ],
  "requiresCompatibilities": ["EC2"]
}

Output

Defines a task to run an Nginx container on ECS EC2 with 512MB memory and 256 CPU units.

ECS Fargate Equivalent

This is the equivalent ECS task definition snippet for running the same container on ECS Fargate.

json

{
  "family": "fargate-task",
  "containerDefinitions": [
    {
      "name": "web",
      "image": "nginx",
      "memory": 512,
      "cpu": 256,
      "essential": true,
      "portMappings": [
        {
          "containerPort": 80,
          "protocol": "tcp"
        }
      ]
    }
  ],
  "requiresCompatibilities": ["FARGATE"],
  "networkMode": "awsvpc",
  "cpu": "256",
  "memory": "512"
}

Output

Defines a task to run an Nginx container on ECS Fargate with 512MB memory and 256 CPU units, using awsvpc networking.

When to Use Which

Choose ECS EC2 when you need full control over the server environment, want to use custom AMIs, or have steady workloads that benefit from reserved EC2 instances. It is also suitable if you want to optimize costs by managing instance usage yourself.

Choose ECS Fargate when you want to focus on deploying containers without managing servers, prefer automatic scaling, or have variable workloads that benefit from pay-per-use pricing. It is ideal for simpler operations and faster deployments.

Key Takeaways

ECS EC2 requires managing servers; ECS Fargate is serverless and managed by AWS.

ECS Fargate charges per task resource usage; ECS EC2 charges for running instances.

Use ECS EC2 for custom server control and steady workloads.

Use ECS Fargate for ease of use, automatic scaling, and variable workloads.

Task definitions differ mainly in compatibility and networking settings.