OAuth 2.0 Authorization ER Diagram Template

This ER diagram template visualizes the entities and relationships that make up the OAuth 2.0 Authorization Code Grant flow — one of the most widely used and secure OAuth grant types. The diagram captures core entities such as the Client Application, Resource Owner, Authorization Server, and Resource Server, along with their key attributes like client_id, redirect_uri, authorization_code, access_token, and refresh_token. Relationships between these entities — including how the client requests authorization, how the authorization server issues codes and tokens, and how the resource server validates access — are clearly mapped to give developers and security architects a structured data-level view of the entire flow.

## When to Use This Template

This template is especially useful when you are designing or documenting the backend data model that supports an OAuth 2.0 implementation. If you are building an identity provider, integrating a third-party login system, or auditing an existing authorization infrastructure, this ER diagram helps you identify how entities relate and where data dependencies exist. Security engineers can use it to spot potential vulnerabilities in token storage or scope management, while backend developers can reference it when designing database schemas for token persistence, session management, and client registration tables.

## Common Mistakes to Avoid

One frequent mistake when diagramming this flow is conflating the sequence of HTTP interactions with the entity relationships. An ER diagram is not a sequence or flow diagram — it should focus on entities, their attributes, and cardinality, not on the order of API calls. Another common error is omitting the Token entity entirely and only modeling the Authorization Code, which misses the critical relationship between issued codes and the resulting access and refresh tokens. Be sure to include scope as an attribute or even a separate entity if your system supports fine-grained permissions, since scope directly constrains what the access token can authorize. Finally, avoid leaving out the expiry and revocation attributes on token entities — these are essential for modeling secure, production-grade OAuth systems and are often overlooked in early-stage diagrams.