Serverless

Serverless is a model in which you deploy individual functions and the provider runs them on demand, allocating capacity per request and billing only for execution time. There are still servers; you simply never see or manage them.

It suits spiky, intermittent and event-driven work particularly well — processing an upload, handling a webhook, running a nightly job. Something invoked a few thousand times a day costs very little and needs no capacity planning at all.

It suits sustained high traffic poorly, where a continuously running server is cheaper, and it suits latency-critical paths poorly because an idle function has to cold start before it can answer. Long-running work and anything needing a persistent connection are awkward too. Read the pricing model before committing: serverless is cheap at low volume and can be startling at high volume.