Function as a service (FaaS)
Function as a Service is the serverless compute model where the deployment unit is a single function with a defined entry point — the provider invokes it in response to events (HTTP request, queue message, scheduled timer) and bills per millisecond of execution. Examples: AWS Lambda, Google Cloud Functions, Azure Functions, Cloudflare Workers.
FaaS is the purest serverless model: no servers to manage, automatic scaling to zero, pay only for actual execution time. The fit is best for short, stateless, event-driven work. The constraints are real: execution time limits (15 minutes on Lambda), cold-start penalty for infrequent invocations, no persistent local state, and a per-invocation overhead that makes high-frequency tight-loop work uneconomic. Modern FaaS variants reduce the constraints — provisioned concurrency eliminates cold starts at a cost; SnapStart pre-snapshots the JVM; Cloudflare Workers run on V8 isolates with sub-ms cold starts. The platform choice matters more than the FaaS-vs-not question for cost and latency.
Related terms
- Serverless
Serverless is the cloud-computing model in which the cloud provider runs and scales the underlying infrastructure transparently — the developer deploys code (functions, containers) and the provider handles servers, capacity, and most operational concerns.
- Edge function
An edge function executes at the CDN's edge locations close to the user — typically with sub-millisecond cold starts (V8 isolates) and ~10-50ms latency advantage vs origin-region functions.
- Webhook
A webhook is an HTTP callback that one service invokes on another when a defined event occurs — typically a POST request with the event payload to a URL the consumer registered.