Deploy a Containerized Application on Fargate with Load Balancing

Architecture Overview

This architecture runs your application as a containerized service on AWS Fargate, which is the serverless compute engine for ECS. You provide a Dockerfile, and the deployment handles building the image, pushing it to ECR, and running it as a Fargate task behind an Application Load Balancer. There are no EC2 instances to patch, scale, or monitor.

The Application Load Balancer serves as the entry point for all traffic. It distributes requests across running Fargate tasks, performs health checks against each task, and automatically deregisters unhealthy containers so ECS can replace them. This gives you a resilient, self-healing deployment without writing any custom health-check logic.

Fargate abstracts away the underlying compute. You specify CPU and memory requirements for your container, and AWS provisions the right amount of capacity. When combined with ECS service autoscaling, the number of running tasks adjusts based on CPU utilization, memory usage, or request count. This means you pay only for the compute your application actually uses.

ECS Cluster and Service

The ECS cluster is the logical grouping for your tasks. The Fargate service within the cluster defines how many copies of your container should run, which subnets to place them in, and how to connect to the load balancer. ECS maintains the desired count by launching new tasks when existing ones fail health checks or are terminated.

ECR Repository and Image Build

The ECR repository stores your Docker image. The deployment builds the image from your local Dockerfile, tags it, and pushes it to ECR. Fargate pulls the image from ECR when launching tasks. This keeps the entire build-push-deploy cycle within AWS, avoiding external registry dependencies.

Application Load Balancer

The ALB provides a stable DNS name and distributes incoming HTTP traffic across healthy Fargate tasks. Target group health checks ensure that only tasks responding correctly receive traffic. You can add path-based routing rules, HTTPS listeners with ACM certificates, or sticky sessions through customization.

Common Customizations

• Add HTTPS: Request an ACM certificate and an HTTPS listener on the ALB to terminate TLS, redirecting HTTP traffic to HTTPS.
• Configure autoscaling: Ask for ECS service autoscaling based on CPU utilization or ALB request count to handle traffic spikes automatically.
• Use a custom domain: Add a Route53 alias record pointing your domain to the ALB so users access your application through a clean URL.
• Add multiple containers: Deploy a sidecar container (like a log router or reverse proxy) alongside your application container in the same task definition.