Which OAuth grant type is primarily used for system-to-system integration?

• A. Authorization Code Flow
• B. Password Grant
• C. Client Credentials Flow
• D. Implicit Flow

Answer: (C)

The Client Credentials Flow is primarily used for system-to-system integration because it allows applications to communicate with each other without the involvement of user credentials. In this flow, the application authenticates itself using its own credentials (usually a client ID and secret) and requests an access token directly from the authorization server. This is particularly suitable for backend services or APIs where user context is not required, enabling the application to perform tasks or access resources on behalf of itself rather than a user.

In contrast, other grant types like Authorization Code Flow and Password Grant involve user interaction and are intended for scenarios where user resources are accessed, requiring user credential verification. The Implicit Flow is tailored for single-page applications where user-interaction is inherent, and it focuses on obtaining tokens without a back-end server exchange. Thus, the Client Credentials Flow stands out for its simplicity and effectiveness in scenarios involving automated systems needing direct access without user involvement.