ECS Express Mode Concepts
What Is Express Mode?
Section titled “What Is Express Mode?” Express Gateway Service
The aws_ecs_express_gateway_service Terraform resource that provisions an ECS service with managed ALB, auto scaling, and simplified configuration for HTTP/HTTPS web applications and APIs. is a simplified deployment model that removes the need to provision separate ALB, target group, and listener resources. You create one resource — aws_ecs_express_gateway_service — and ECS provisions a managed , configures health checks, sets up auto scaling, and assigns a unique Application URL
The unique Express-provisioned HTTPS URL on *.ecs.<region>.on.aws used for all normal application traffic. on *.ecs.<region>.on.aws.
In classic ECS, you wire together aws_lb, aws_lb_target_group, aws_lb_listener, aws_ecs_service, and aws_appautoscaling_target. Express Mode collapses all of this into one resource.
The hosts up to 25 Express services in the same VPC
Virtual Private Cloud — an isolated virtual network within AWS where resources are deployed. using Host header routing. The first service in a VPC determines whether the ALB is internet-facing or internal.
Express Mode vs Classic ECS
Section titled “Express Mode vs Classic ECS”| Dimension | Express Mode | Classic ECS |
|---|---|---|
| Inputs required | Single | Separate ALB, target group, listener, service, and scaling resources |
| Infrastructure wiring | Fully managed — no cross-resource references | Manual — you connect LB → target group → service |
| Typical user | Developers wanting fast HTTP/HTTPS deployment | Platform teams needing full networking control |
| Subnet model | Single list for both ALB and tasks | Separate subnet configuration for ALB and tasks |
| Health checks | ALB target group only via | ALB health check plus optional container |
| Deployment strategy | Rolling with automatic rollback on health failure | Rolling, blue/green, or external controller |
| Scaling | Built-in target tracking via | Separate |
| Protocol support | HTTP/HTTPS only | HTTP, HTTPS, gRPC, TCP, UDP, TLS |
Supported Workloads
Section titled “Supported Workloads”Express Mode works for:
- REST / OpenAPI APIs — stateless request/response over HTTPS
- Stateless web applications — frontends, dashboards, documentation sites
- Rapid prototyping — public HTTPS endpoint without infrastructure boilerplate
- Developer self-service — deploy HTTP services without platform team help
Unsupported Workloads
Section titled “Unsupported Workloads”Use classic ECS for these:
- Batch / queue workers — no HTTP endpoint, no ALB needed
- gRPC — ALB terminates HTTP/2, breaking gRPC streaming
- Raw TCP/UDP — Express Mode only handles HTTP/HTTPS
- Non-HTTP services — anything that cannot respond to ALB health checks
Single Subnet Limitation
Section titled “Single Subnet Limitation”Classic ECS lets you place the ALB in public subnets while running tasks in private subnets. Express Gateway Service
The aws_ecs_express_gateway_service Terraform resource that provisions an ECS service with managed ALB, auto scaling, and simplified configuration for HTTP/HTTPS web applications and APIs. does not support this split — it uses one subnet list for both.
- Public Subnet
A subnet with a route to an Internet Gateway, enabling resources to have public IP addresses and internet access. (route to Internet Gateway
A VPC component that enables communication between resources in a VPC and the internet. ) → internet-facing ALB, tasks with public IPs - Private subnets (no IGW route) → internal ALB, reachable only within the VPC
Virtual Private Cloud — an isolated virtual network within AWS where resources are deployed.