Health checks with readiness + liveness

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                  import type { Request, Response } from 'express';
import { pool } from '../db/pool';

export function liveness(_req: Request, res: Response) {
  res.status(200).json({ ok: true });
}

export async function readiness(_req: Request, res: Response) {
  try {
    await pool.query('SELECT 1');
    res.status(200).json({ ok: true });
  } catch {
    res.status(503).json({ ok: false });
  }
}

One /health endpoint is ambiguous: is the process alive, or is it actually ready to serve traffic? I split them. Liveness answers ‘should the orchestrator restart me?’ and is usually just ‘the event loop is alive’. Readiness answers ‘can I accept traffic?’ and checks dependencies like DB/Redis. I also flip readiness to false immediately when shutdown begins so the load balancer drains connections before we start force-closing sockets. When these endpoints are consistent across services, infrastructure becomes easier to automate. The goal is fewer noisy incidents during rolling deploys and transient dependency failures—not building a perfect health oracle.

Mateo Rodriguez

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Health checks with readiness + liveness

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