Serverless
faas, function-as-a-service, serverless computingDefinition
A hosting model where you deploy a function or a container rather than a server, the platform starts an instance when a request arrives and stops it when traffic stops, and you are billed for execution rather than for uptime
The servers did not go away; the capacity planning did. What you give up in exchange is anything that assumed a long-lived process — an in-memory cache that survives requests, a file written to disk, a WebSocket held open, a warm connection pool. Most serverless surprises are one of those four discovering that the box it lived in is gone.
Renting execution instead of renting a machine. The pricing is the honest description: you pay when something happens.
Avoid: reading it as strictly cheaper. Scaling to zero is excellent for spiky or occasional work and poor for steady load, where a small always-on instance wins on both cost and cold starts. This site runs on a container that stays up, because a garden with steady readers is the second case.