docker-expert

Multi-stage builds separate dependency installation, compilation, and runtime into distinct stages, copying only necessary artifacts into the final stage. Combining this with distroless or Alpine base images and cleaning package manager caches in the same RUN layer significantly shrinks images.

Create a dedicated user with a specific UID/GID using addgroup and adduser, then set the USER directive before CMD. Also copy files with --chown so the application user owns its working directory.

Yes, Compose supports healthcheck blocks with test commands, intervals, and retries. Use depends_on with condition: service_healthy to enforce startup ordering so dependent services wait until dependencies are ready.

Slow builds usually come from poor layer ordering, large build contexts, or missing cache strategy. Copy dependency manifests before source code, add a comprehensive .dockerignore, and use BuildKit cache mounts for package managers.

Docker Compose suits single-host development and small deployments, while Kubernetes is needed for multi-node orchestration, autoscaling, and advanced service discovery. This Skill handles Docker and Compose; Kubernetes questions should go to a Kubernetes-focused expert.