Fargate and EC2 in AWS ECS
When running containers on Amazon ECS (Elastic Container Service), we choose a launch type that determines where and how our containers run. The two main options are AWS Fargate and EC2. Both run the same container images and use the same task definitions, but they differ in how the underlying compute is provisioned and managed.
AWS Fargate
AWS Fargate is a serverless compute engine for containers. We define our tasks, and Fargate provisions and manages the underlying infrastructure automatically. There are no servers to patch, scale, or maintain.
Key characteristics:
- No server management: AWS handles the provisioning, patching, and scaling of the underlying compute.
- Per-task resource allocation: We specify the CPU and memory each task needs, and Fargate allocates exactly that.
- Pay-per-use billing: We pay for the vCPU and memory that our running tasks consume, billed per second.
- Isolation: Each task runs in its own isolated environment, improving security.
- Fast scaling: Tasks launch without waiting for EC2 instances to be provisioned or added to a cluster.
Best for:
- Teams that want to focus on applications rather than infrastructure.
- Workloads with variable or unpredictable traffic.
- Microservices and batch jobs where operational simplicity matters most.
- Getting started quickly without capacity planning.
EC2 Launch Type
With the EC2 launch type, our containers run on a cluster of Amazon EC2 instances that we provision and manage. ECS schedules tasks onto these instances, but we are responsible for the instances themselves.
Key characteristics:
- Full control: We choose the instance types, AMIs, and configuration to match our workload.
- Access to the host: We can install agents, use custom kernel parameters, or attach specialized hardware.
- Cost optimization at scale: We can use Reserved Instances, Savings Plans, or Spot Instances to reduce cost for steady, high-density workloads.
- Shared instance resources: Multiple tasks can be packed onto the same instance to maximize utilization.
- Operational responsibility: We manage instance patching, scaling (via Auto Scaling Groups), and capacity.
Best for:
- Workloads that require specific instance types, GPUs, or specialized hardware.
- Large, steady-state workloads where careful capacity planning lowers cost.
- Applications needing host-level access or custom configurations.
- Existing EC2 infrastructure investments and reserved capacity.
Fargate vs EC2
| Aspect | Fargate | EC2 |
|---|---|---|
| Infrastructure management | Managed by AWS | Managed by us |
| Server patching & scaling | Handled automatically | Our responsibility |
| Billing model | Per task (vCPU + memory, per second) | Per EC2 instance (running time) |
| Control over host | None | Full control |
| Instance/hardware choice | Not applicable | Custom instance types, GPUs, etc. |
| Scaling speed | Fast, per-task | Depends on instance provisioning |
| Cost efficiency | Great for variable workloads | Great for steady, high-density workloads |
| Operational overhead | Minimal | Higher |
| Best use case | Simplicity, variable traffic | Control, cost tuning at scale |
How to Choose
- Choose Fargate when we want minimal operational overhead, faster time to market, and flexible scaling without managing servers. It is ideal for variable workloads and teams that prefer to avoid infrastructure management.
- Choose EC2 when we need fine-grained control over the compute environment, require specialized hardware, or can achieve significant cost savings with Reserved or Spot Instances for large, predictable workloads.
Many organizations use a mix of both: Fargate for spiky or unpredictable services and EC2 for steady, cost-sensitive, or hardware-specific workloads. Because both launch types share the same task definitions, we can move workloads between them with relatively little effort.
Conclusion
Fargate and EC2 give us two ways to run containers on ECS with a trade-off between simplicity and control. Fargate removes infrastructure management and is ideal for agility and variable workloads, while EC2 offers deeper control and cost optimization for steady, specialized workloads. Understanding these differences helps us pick the right launch type — or combination — for each application.