How do you implement health checks for microservices?

Health checks are endpoints that report the operational status of a service.

Types of health checks:

• Liveness: Is the service running?
• Readiness: Can the service handle requests?
• Startup: Has the service finished initializing?

Implementation example:

app.get('/health', (req, res) => {
  const healthCheck = {
    uptime: process.uptime(),
    status: 'OK',
    timestamp: Date.now(),
    checks: {
      database: checkDatabase(),
      externalAPI: checkExternalAPI()
    }
  };
  res.status(200).send(healthCheck);
});

Best practices:

• Keep health checks lightweight
• Check critical dependencies
• Return appropriate HTTP status codes
• Include relevant diagnostic information