Sequence Diagrams

Examples of sequence diagrams showing interactions between different actors

Basic Sequence Diagram

sequenceDiagram
    participant User
    participant Browser
    participant Server
    participant Database
    
    User->>Browser: Enter URL
    Browser->>Server: HTTP Request
    Server->>Database: Query Data
    Database-->>Server: Return Results
    Server-->>Browser: HTTP Response
    Browser-->>User: Display Page
  

Authentication Flow

sequenceDiagram
    actor User
    participant App
    participant Auth as Auth Service
    participant DB as Database
    
    User->>App: Login (email, password)
    App->>Auth: Validate Credentials
    Auth->>DB: Check User
    DB-->>Auth: User Data
    
    alt Valid Credentials
        Auth-->>App: JWT Token
        App-->>User: Login Success
        App->>App: Store Token
    else Invalid Credentials
        Auth-->>App: Error
        App-->>User: Login Failed
    end
  

API Communication

sequenceDiagram
    participant C as Client
    participant G as Gateway
    participant A as Auth Service
    participant S as API Server
    participant D as Database
    
    C->>G: Request + Token
    G->>A: Validate Token
    A-->>G: Token Valid
    
    G->>S: Forward Request
    activate S
    S->>D: Query Data
    D-->>S: Result Set
    S-->>G: Response
    deactivate S
    
    G-->>C: Final Response
    
    Note over C,D: All communication is encrypted
  

Loops and Conditions

sequenceDiagram
    participant Client
    participant Server
    participant Cache
    participant DB
    
    Client->>Server: Request Data
    
    loop Check Cache First
        Server->>Cache: Get from Cache
        alt Cache Hit
            Cache-->>Server: Cached Data
            Server-->>Client: Return Data
        else Cache Miss
            Server->>DB: Query Database
            DB-->>Server: Fresh Data
            Server->>Cache: Update Cache
            Server-->>Client: Return Data
        end
    end
  

Parallel Processing

sequenceDiagram
    participant User
    participant System
    participant ServiceA
    participant ServiceB
    participant ServiceC
    
    User->>System: Submit Request
    
    par Parallel Processing
        System->>ServiceA: Process A
        and
        System->>ServiceB: Process B
        and
        System->>ServiceC: Process C
    end
    
    ServiceA-->>System: Result A
    ServiceB-->>System: Result B
    ServiceC-->>System: Result C
    
    System->>System: Aggregate Results
    System-->>User: Combined Response
  

Activation Boxes

sequenceDiagram
    participant Browser
    participant Server
    participant Worker
    participant Queue
    
    Browser->>+Server: Upload File
    Server->>Server: Validate File
    Server->>+Queue: Add Job
    Queue-->>-Server: Job ID
    Server-->>-Browser: Upload Accepted
    
    Queue->>+Worker: Process Job
    Worker->>Worker: Transform File
    Worker->>Worker: Optimize
    Worker-->>-Queue: Job Complete
    
    Browser->>+Server: Check Status
    Server->>Queue: Get Job Status
    Queue-->>Server: Completed
    Server-->>-Browser: File Ready
  

Message Types

sequenceDiagram
    participant A as Service A
    participant B as Service B
    
    A->>B: Sync Request
    B-->>A: Sync Response
    
    A->>+B: Async Request
    Note right of B: Processing...
    B-->>-A: Async Response
    
    A--xB: Failed Request
    B-)A: Fire and Forget
    
    A--)B: Async Message
    
    Note over A,B: Different arrow types demonstrate various communication patterns