Docker Compose — Multi-Container Apps
4 Topics
1
What is Docker Compose and When to Use It
Local multi-service orchestration tool overview.
Interviewers often ask how Docker Compose differs from Kubernetes or Docker Swarm. Focus on explaining that Compose is a local development and testing orchestration tool that consolidates multi-container run commands into a single declarative configuration file, whereas Kubernetes is a production cluster manager.
2
Writing a docker-compose.yml — Every Field Explained
Understanding services, networks, volumes, environment, and builds.
Be prepared to write a basic Docker Compose YAML file on a whiteboard. Understand how fields like `build`, `ports`, `depends_on` (including condition checks for database readiness), `environment`, and `volumes` are structured and function.
3
Networking Between Services in Docker Compose
Automatic network setup and domain name sharing.
Understand service discovery in Docker Compose. Interviewers will ask: how does Service A resolve the address of Service B? Be ready to explain the automatic creation of a default bridge network, embedded DNS resolution, and network segmentation (e.g., placing frontends and backends on isolated subnets).
4
Docker Compose in CI/CD — Testing Multi-Service Apps Locally
Building testing environments and teardown scripts.
Interviewers love to ask how you optimize integration testing loops in pipelines. Know how to run Compose in non-interactive mode (`-d`), use the `--exit-code-from` flag to run test runners and propagate exit codes, and clean up test resources to prevent disk leaks.