An engineer must implement a public cloud solution that enables a company to place all its infrastructure and its end-user applications in the cloud…

Software as a Service (SaaS) delivers complete, ready-to-use applications that run on the provider’s cloud infrastructure. The provider operates and maintains the entire application stack—servers, OSs, middleware, and the application itself—so the customer no longer installs, patches, or manages any software or underlying infrastructure. This exactly matches the requirement to “place all infrastructure and end-user applications in the cloud, eliminating the need for software application management and maintenance.”

B. PaaS – Off-loads infrastructure and middleware, but customer still builds, deploys, and maintains the application code.

C. IaaS – Only virtualized hardware is provided; OS, middleware, and applications remain the customer’s responsibility.

D. FaaS – Event-driven code snippets run in the cloud; does not provide full-stack applications or relieve customers of application lifecycle management.

1. Cisco Press, Understanding Cisco Cloud Fundamentals (CLDFND 210-451 Official Cert Guide), Ch. 2 “Cloud Service Models,” pp. 26-28: describes SaaS as provider-managed full application stack eliminating customer maintenance.

2. Cisco Systems, “Cisco Cloud Computing – Data Center Strategy, Architecture, and Solutions,” White Paper, Section 2.2, pp. 42-43: defines SaaS and contrasts it with PaaS and IaaS responsibilities.

3. NIST Special Publication 800-145, “The NIST Definition of Cloud Computing,” p. 2: SaaS definition—consumer uses provider’s applications running on a cloud infrastructure and manages neither infrastructure nor application platform.