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How do you design liveness and readiness health-check endpoints?

Q: How do you design liveness and readiness health-check endpoints?

**TL;DR.** A **liveness** probe answers "is the process alive?" and must stay **cheap** so orchestrators don't kill a busy-but-healthy app. A **readiness** probe answers "can it serve traffic?" and checks **dependencies** (DB, cache); failing it **removes the instance from the load balancer** without restarting it. /livez (liveness) cheap, no deps fail ⇒ restart pod /readyz (readiness) check DB/cache</text

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Understand the problem

Distinguishing 'is the process alive' from 'can it serve traffic'.

nodejsopshealth-checkkubernetes

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Read the code

Separate liveness and readiness

let ready = true;
app.get('/livez', (req, res) => res.sendStatus(200));   // cheap, no deps

app.get('/readyz', async (req, res) => {
  if (!ready) return res.sendStatus(503);               // draining
  try { await db.query('SELECT 1'); res.sendStatus(200); }
  catch { res.sendStatus(503); }                         // dep down → drop from LB
});

process.on('SIGTERM', () => { ready = false; /* then drain + close */ });

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