The document discusses efficient Spring Data REST development. It defines REST as a software architectural style using HTTP to access and manipulate web resources represented as text. It describes the REST architectural style of using stateless operations like GET, POST, PUT, PATCH and DELETE on a resource's URL. It also discusses ETags for caching and conditional requests, generating REST events through annotated handlers or application listeners, using projections and excerpts for customized views of resources, and reactive access to repositories for streaming results.