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Lesson 7 — Health checks: dependencies
Check the things you depend on
A service is only healthy if what it needs works too: the database, the cache, other APIs. A dependency health check tests each one and reports which are down. A load balancer (the server that spreads traffic over your machines) stops sending users to an instance that reports "unhealthy".
Note: real DevOps tools (CI servers, load balancers, Docker, Kubernetes) cannot run in your browser, so this exercise is a small plain-JS simulation of the logic those tools use.
Why it matters: "the app is up but the database is not" is still an outage — the check must say so.
Fill down with the names of dependencies whose value is false, then return the status line.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledgeA quick 3-question quiz on this lesson — instant feedback.