Question 1

Which Docker Compose file version should I use?

Accepted Answer

For most modern projects, omit the 'version' key entirely — it is deprecated as of Compose Specification (supported by Docker Compose v2+). If you must support older tooling, use version: '3.8'. The version field historically controlled which features were available, but the Compose Specification has unified this into a single schema.

Question 2

What is the difference between depends_on and healthcheck?

Accepted Answer

depends_on controls start order — a service will wait for its dependency to be started (not healthy). Combining depends_on with condition: service_healthy and a healthcheck block makes a service wait until the dependency actually passes its health probe. Without a healthcheck, service_healthy falls back to service_started, which may be too early for databases that need time to initialise.

Question 3

What is the difference between named and anonymous volumes?

Accepted Answer

Named volumes (declared under the top-level 'volumes' key) persist data across container restarts and can be inspected with docker volume ls. Anonymous volumes (just a container path like /var/lib/data) are created automatically but not reusable between containers and are removed when you run docker compose down -v. Use named volumes for databases and any data you want to keep.

Question 4

Should I use env_file or environment in my Compose file?

Accepted Answer

Use env_file to load variables from an external .env file (e.g. env_file: .env.production). This keeps secrets out of the Compose file and out of version control. Use environment to set non-secret config values inline (e.g. NODE_ENV: production). Never commit real credentials in the environment block — use env_file or Docker Secrets instead.

Question 5

How do services communicate with each other inside Docker Compose?

Accepted Answer

Services in the same Compose file are automatically placed on a shared default network. Each service is reachable by its service name as the hostname (e.g. a 'db' service is reachable at db:5432 from other containers). You can define custom networks under the top-level 'networks' key to isolate groups of services or connect to external networks.

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