# Knowledge Check: Docker Compose

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**1. What does `depends_on` actually guarantee — and NOT guarantee?**

*Answer:* It guarantees START order (the dependency's container is started before the dependent
service's). It does NOT guarantee the dependency is actually READY/healthy yet — a real,
common source of race conditions in production Compose files.

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**2. Do you need to manually run `docker network create` for services in the same Compose file
to reach each other by name?**

*Answer:* No — Compose automatically creates a shared network for all services defined in the
file, and they can reach each other by service name immediately.

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**3. What does `docker compose down` clean up, that plain `docker compose stop` would not?**

*Answer:* `down` removes the containers AND the network Compose created; `stop` only stops the
containers, leaving them (and the network) in place to be restarted later.

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**4. Does Compose introduce any concept that isn't already just automating `docker run`/
`docker network` commands you already know?**

*Answer:* No — every Compose service maps directly onto concepts already covered
(image, ports, networking); Compose automates and declaratively describes them, it doesn't add
new underlying mechanisms.

## Instructor Notes

**Facilitation:** Question 1 is worth real emphasis — it's a genuine, common production
mistake worth preventing early.

**Approximate timing:** 5 minutes.