Run Multiple Containers with ECS Fargate Task: Ghost CMS + Webhook Receiver with ECR on AWS

In this build session, I extended the Ghost ECS Fargate deployment from the previous video by adding a second container to the same task — a FastAPI webhook receiver that listens for Ghost member events. The idea: Ghost fires events when members sign up, posts go live, or tiers change. Without something listening, those events vanish. So we added a small receiver running alongside Ghost in the same Fargate task, communicating over localhost. 🧱 What We're Building We extended the single-container Ghost deployment into a multi-container ECS task: ➜ Ghost runs as the primary container on port 2368 ➜ A FastAPI webhook receiver runs on port 8000 in the same task ➜ Both containers share the Fargate task's network namespace ➜ Ghost sends member events to localhost:8000/webhook ➜ The webhook receiver logs everything to CloudWatch ➜ The receiver is internal only — not exposed through the ALB or the internet 🔍 What We Covered ✅ Why multi-container tasks exist and when to use them ✅ Building a FastAPI webhook receiver and testing it locally ✅ Creating an ECR repository and pushing a custom image ✅ Updating the ECS task definition to run two containers ✅ Essential vs non-essential containers and what happens when one crashes ✅ How containers in the same task communicate over localhost ✅ Security group behavior — why port 8000 stays blocked from outside ✅ Configuring Ghost webhooks to fire on member events ✅ Verifying webhook delivery in CloudWatch Logs 🧩 Where This Breaks Down The coupling is deliberate — both containers scale, deploy, and restart together. That works for prototyping. It stops working when Ghost needs to scale on HTTP traffic and the webhook processor needs to scale on event volume. Future sessions will cover: ➜ Splitting into separate ECS services ➜ ECS Service Connect for private inter-service routing ➜ Independent autoscaling per service Subscribe for more practical AWS build sessions. Full Terraform code and step-by-step walkthrough on the blog: https://brainyl.cloud/ghost-ecs-farga... — Build with Brainyl