A cloud infrastructure function that can grow and shrink to meet peak demand requirements quickly is known as:

Elasticity, as defined by NIST in SP 800-145, is the capability to rapidly provision and release computing resources to scale outward or inward commensurate with demand. This allows cloud workloads to grow during peak periods and shrink when demand subsides, optimizing cost and performance simultaneously. It directly describes infrastructure that can expand and contract quickly to match peak demand requirements.

Federation refers to linking separate identity systems or organizational domains to enable shared access and single sign-on, not to scaling compute resources.

Automation describes the use of scripts or orchestration tools to reduce manual tasks, but it does not inherently define dynamic resource scaling in response to demand.

Caching stores frequently accessed data in fast-access storage to reduce retrieval latency but does not grow or shrink infrastructure capacity based on workload demand.