sequenceDiagram
    participant Client
    participant Service as service/db/session
    participant Table as infra/table/sessions
    participant DB as Database (ORM)
    participant Coordinator as Cluster Coordinator
    participant Cache as USER_SESSIONS Cache

    Note over Client,Cache: Session Set Operation
    Client->>Service: set(session_id, access_token)
    Service->>Table: set(session_id, access_token)
    Table->>DB: find().filter(SessionId).one()
    DB-->>Table: Option<Model>
    alt Session exists
        Table->>Table: Convert to ActiveModel
        Table->>DB: update(access_token, updated_at)
    else Session not found
        Table->>Table: Create new ActiveModel
        Table->>DB: insert(new session)
    end
    DB-->>Table: Result
    Table-->>Service: Ok(())
    Service->>Coordinator: put_into_db_coordinator(key, empty_bytes)
    Service->>Cache: insert(session_id, access_token)
    Service-->>Client: Ok(())

    Note over Client,Cache: Session Get Operation
    Client->>Service: get(session_id)
    Service->>Cache: get(session_id)
    alt Cache hit
        Cache-->>Service: access_token
        Service-->>Client: Ok(access_token)
    else Cache miss
        Service->>Table: get(session_id)
        Table->>DB: find().filter(SessionId).one()
        DB-->>Table: Option<Model>
        alt Found
            Table-->>Service: Some(session)
            Service->>Cache: insert(session_id, access_token)
            Service-->>Client: Ok(access_token)
        else Not found
            Table-->>Service: None
            Service-->>Client: Error("Session not found")
        end
    end

    Note over Client,Cache: Session Watch & Sync
    Coordinator->>Service: watch() event
    alt Put Event
        Service->>Table: get(session_id)
        Table->>DB: find().filter(SessionId).one()
        DB-->>Table: Option<Model>
        Table-->>Service: Some(session)
        Service->>Cache: insert(session_id, access_token)
    else Delete Event
        Service->>Cache: remove(session_id)
    end