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World A4: Containers in the Cloud

ECS: tasks and services

You will learn: how ECS runs containers from a recipe card, and keeps them running.

Checked with AWS 2026-11 on 1 Nov 2026

The problem

Tap each point on the timeline.

Containers crash. Someone must notice and start a new one, every time. Tap the story. Who could do it at 2 a.m.?

Watch

ECS: Elastic Container Service: the mall's manager that runs your containers to a plan. is the mall’s manager for containers. You give it a plan. It keeps the plan true, day and night. Put its steps in order.

First step at the top. Put these in order. Use the arrows, or drag.

  • ECS starts 2 tasks from the card
  • Write the recipe card (task definition)
  • Create a service: keep 2 running
  • Register it with ECS

Watch

The recipe card is a Task definition: ECS's recipe card: which image, how much CPU and memory, which ports and settings.. It is JSON. Tap the line that says which image to run.

Tap the line that picks the image.

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Try it

A running copy of the card is a task. A ECS service: A promise to keep N copies of a task running. One stops? ECS starts a new one. keeps N tasks alive. Which one holds each setting?

Drag a card into a box. Or tap the card, then tap the box.

      Predict

      The service wants 2 tasks. At 2 a.m. one crashes. What happens?

      Check

      The CLI lists running tasks. Here is the official example’s answer. Tap each task.

      Tap each running task.

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      You did it!

      You can now write a task definition, and let a service keep it running.

      Go deeper (optional)

      ECS itself has no extra charge. You pay for what tasks run on: Fargate (next lesson) or EC2 servers. A new card version is a revision: kedai-web:2. Point the service at it, and ECS rolls new tasks in, old ones out.