Stage in the evolution of cloud abstraction after IaaS (e.g. EC2, scales on OS), CaaS (e.g. ECS, scales on containers), and PaaS (e.g. Heroku, scales on application). FaaS scales at the granularity of individual functions: one application contains many independently scaled functions. Removes the need to manage servers or DevOps — just deploy code. Benefits: reduced operational cost, scales to the provider's limits, and encourages better code because faster code is cheaper and tightly-coupled large code becomes impractical.