---
config:
    layout: elk
---

erDiagram
    User ||--o| Profile : "has profile"
    User ||--o{ Follow : "follows"
    User ||--o{ Follow : "followed by"
    Profile ||--o{ Avatar : "has avatar history"

    %% Cross-schema: defined in full in auth.mmd / media.mmd
    Avatar }o--|| Photo : "uses photo"

    Profile {
        uniqueidentifier UserProfileID PK
        uniqueidentifier UserAccountID "FK, UK"
        nvarchar Biography
    }

    Follow {
        uniqueidentifier UserFollowID PK
        uniqueidentifier UserAccountID FK
        uniqueidentifier FollowingID FK
        datetime CreatedAt
    }

    Avatar {
        uniqueidentifier UserAvatarID PK
        uniqueidentifier UserProfileID FK
        uniqueidentifier PhotoID FK
        datetime2 ValidFrom
        datetime2 ValidTo "nullable; at most one row per UserProfileID has ValidTo IS NULL (active avatar)"
    }