# REST API glossary: Master level

7 REST API terms at the Master level, each with a short definition and a link to its full page.

Updated: September 27, 2026

[Study these as flash cards](https://www.ask-codey.com/decks/rest-api/master)

- [API-First Design](https://www.ask-codey.com/glossary/api-first-design): Agreeing on the API contract before writing the implementation.
- [gRPC](https://www.ask-codey.com/glossary/grpc): A fast, binary, contract-first API style often used between services.
- [HATEOAS](https://www.ask-codey.com/glossary/hateoas): Responses include links to the next possible actions.
- [HTTP/2 and HTTP/3](https://www.ask-codey.com/glossary/http-2-and-http-3): Newer HTTP versions that send many requests at once over one connection.
- [Mutual TLS](https://www.ask-codey.com/glossary/mutual-tls): Both client and server present certificates to prove who they are.
- [Richardson Maturity Model](https://www.ask-codey.com/glossary/richardson-maturity-model): A four-level scale of how fully an API uses REST ideas.
- [Server-Sent Events](https://www.ask-codey.com/glossary/server-sent-events): A response kept open so the server can push a stream of events.

- Previous level: [Freelancer](https://www.ask-codey.com/glossary/subjects/rest-api/freelancer)

[Every REST API term, by level](https://www.ask-codey.com/glossary/subjects/rest-api)

Source: https://www.ask-codey.com/glossary/subjects/rest-api/master