Cache-aside pattern

sequenceDiagram
    participant App
    participant Cache as Redis
    participant DB as Database

    App->>Cache: GET user:42
    alt Cache hit
        Cache-->>App: Cached value
    else Cache miss
        Cache-->>App: nil
        App->>DB: SELECT user row
        DB-->>App: Row data
        App->>Cache: SETEX user:42 300
    end