35. Graceful shutdown

On deployment or restart, a process typically receives `SIGTERM`. A graceful shutdown stops accepting new connections, waits for in-flight requests to finish, closes database pools and sockets, then exits — instead of dying mid-request and corrupting state or dropping responses.

js
const server = app.listen(3000);

process.on("SIGTERM", async () => {
  console.log("SIGTERM received, shutting down");
  server.close(() => console.log("http server closed"));
  await pool.end(); // close db connections
  process.exit(0);
});

Container orchestrators (Kubernetes, ECS) send `SIGTERM` and then wait a grace period before sending a hard `SIGKILL` — if your shutdown handler takes longer than that window, work is killed anyway, so it should be bounded and fast.

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