TOPIC OVERVIEW

Docker/Compose

Defining and running a multi-container application as a single, declarative unit.

10 QuestionsIntermediateHigh Priority ~11 min read

A docker-compose.yml file declares services (each corresponding to a container), along with the networks and volumes a whole application stack needs — running docker compose up builds and starts everything together, with the connections between services already wired up. Services on the same Compose network can reach each other simply by service name, resolved through Docker's built-in DNS, with no manual network configuration required.

depends_on controls the order services start in, but not whether a dependency is actually ready to accept connections — a database container being 'started' doesn't mean it's finished initializing, which is a very common source of race-condition bugs in Compose setups; healthchecks are the real fix, letting a service wait until a dependency reports itself genuinely ready rather than just running. Compose is squarely a local development and testing tool — for production orchestration at real scale (multiple hosts, self-healing, rolling deployments), something like Kubernetes takes over.

What you'll walk away knowing

What a docker-compose.yml file declares, and what docker compose up actually does with it

How services on the same Compose network reach each other by name, without manual network config

Why depends_on controls startup order but not actual readiness, and what fixes that gap

Where Compose's role ends and a real orchestrator like Kubernetes becomes necessary

1What problem does Docker Compose solve?ExpertHigh 2What are the top-level sections in a docker-compose.yml file, and what does each do? (Demonstrates familiarity with the file's structure.)ExpertHigh 3What's the difference between depends_on and links?ExpertHigh 4How do you handle environment-specific configurations (dev, staging, production)?ExpertHigh 5What's the difference between Docker Compose and Docker Swarm?ExpertHigh 6You need to deploy a Node.js application that uses a MongoDB database and a Redis cache. How would you set this up using Docker Compose?ExpertHigh 7How would you manage dependencies between services to ensure correct startup order?ExpertHigh 8How do you scale a service using Docker Compose?ExpertHigh 9How do you handle persistent storage for databases?ExpertHigh 10How do you manage sensitive data like passwords and API keys?ExpertHigh 11Write a docker-compose.yml file to set up a local development environment for a full-stack application (e.g., a React frontend, a Node.js/Express API, and a PostgreSQL database). ExpertHigh

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