All 7 Amazon ECS (Elastic Container Service) questions
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What is Amazon ECS and why would you use it? What is the difference between ECS Fargate launch type and ECS EC2 launch type? How does an ECS service maintain the desired number of running tasks? How does networking work for containers running in ECS, particularly with the awsvpc network mode? How does ECS Service Auto Scaling work to handle varying application load? What deployment strategies does ECS support for updating running services with minimal downtime?
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What is a task definition in ECS and what does it contain?

Intermediate

Answer

A task definition is a blueprint that describes how a container should run, including which Docker image to use, how much CPU and memory to allocate, networking configuration, environment variables, and logging settings, and ECS uses this definition every time it launches a new task or scales your service up.
{
  "family": "web-app",
  "containerDefinitions": [{
    "name": "web",
    "image": "myrepo/web-app:latest",
    "memory": 512,
    "cpu": 256
  }]
}
Real-world example A development team updates a task definition to point to a new Docker image version, then deploys that updated task definition to their ECS service, which gradually replaces old running containers with new ones.

Common follow-ups: How do you update a running service to use a new task definition revision?;Can a single task definition run multiple containers together?

Elastic Container Registry (ECR);IAM
All 7 Amazon ECS (Elastic Container Service) questions