What is FaaS?

FaaS, short for Function as a Service, is a category of cloud computing that allows developers to run individual pieces of code (functions) in response to events without managing the underlying server infrastructure. Each function is stateless, typically short-lived, and executed only when triggered by an event such as an HTTP request, a file upload, a database change, or a scheduled timer. The cloud provider handles all runtime provisioning, scaling, fault tolerance, and logging. Billing is based solely on execution time and resource consumption per invocation, often with a free tier for low usage.

A function is packaged as a unit of deployment, often bundled with its dependencies into a zip file or container image. When invoked, the provider allocates a lightweight runtime environment, executes the function, and tears down the environment shortly after completion. Cold starts occur when a function is invoked after a period of inactivity and the runtime must be initialized from scratch. Many FaaS platforms, such as AWS Lambda (launched 2014), Google Cloud Functions, and Azure Functions, offer integration with API gateways, message queues, and storage services to form event-driven architectures.

FaaS belongs to the broader serverless computing paradigm, where the cloud vendor abstracts servers away from the developer. It differs from Platform as a Service (PaaS) because the developer does not manage any running application processes or containers; the function is the unit of scale. FaaS is well-suited for microservices, data processing pipelines, webhook handlers, and IoT backends. It is not ideal for long-running or stateful workloads due to execution timeout limits (commonly 5 to 15 minutes) and ephemeral storage constraints.