Web Dev//API//external API

Pattern where your app makes HTTP requests directly to a third-party service. The service doesn't run inside your server. It lives somewhere else, and you consume it via HTTP.

Pattern where your app makes HTTP requests directly to a third-party service. The service doesn't run inside your server. It lives somewhere else, and you consume it via HTTP.

Your app is responsible for everything: timeouts, retries, error handling, authentication, and managing state between calls

The request happens synchronously inside your backend handler (or Vercel Function). If the external service is slow, your function waits, and if it waits too long, you hit the timeout.

Examples: Gmail API, Google APIs, Resend (email), Sentry (errors), PostHog (analytics), Upstash (Redis), Pinecone (vectors), Supabase. All are external APIs that your app calls via HTTP

OAuth 2.0 is the standard auth pattern: the user gives permission to the external service, the service gives your app a token

For heavy batch work against external APIs (e.g. thousands of Gmail calls), a single function will timeout. That's where event-driven processing takes over.