HTTP keep-alive agent for outbound calls

10729 views

                  import https from 'node:https';

export const httpsAgent = new https.Agent({
  keepAlive: true,
  maxSockets: 50,
  timeout: 30_000
});

export function fetchWithAgent(url: string, init: RequestInit = {}) {
  return fetch(url, { ...init, agent: httpsAgent as any });
}

Creating a new TCP/TLS connection for every request is slow and it adds load on both sides. For high-traffic services calling a small set of upstreams, keep-alive reduces latency and CPU dramatically. I configure an https.Agent with sensible maxSockets and a timeout, then reuse it across requests. The gotcha is that keep-alive can mask DNS changes, so idle timeouts should be reasonable and you shouldn’t cache connections forever. This isn’t a micro-optimization—I’ve seen it reduce p95 latency meaningfully when a service makes multiple downstream calls per request. It’s also a nice ‘free’ win once timeouts and circuit breakers are in place.

Mateo Rodriguez

More from Mateo Rodriguez

HTTP keep-alive agent for outbound calls

0 Comments

More from Mateo Rodriguez