graph TD subgraph "End-User" Client[📱/💻 Client Application] end

subgraph "AWS Cloud (ap-northeast-2)"
    ALB
    subgraph "Amazon EC2"
        SpringBoot
        FastAPI
    end
    subgraph "Data Persistence Layer"
        RDS
        S3
        VectorDB
    end
end

subgraph "External Services"
    Kakao[Kakao Authentication API]
    GoogleAI[Google Cloud AI Platform<br/>(Vision API / Gemini)]
end

%% Data Flows
Client -- HTTPS Request --> ALB
ALB -- HTTP --> SpringBoot

SpringBoot -- "1. Kakao Redirect" --> Client
Client -- "2. User Consent" --> Kakao
Kakao -- "3. Auth Code" --> SpringBoot
SpringBoot -- "4. Token Request" --> Kakao
Kakao -- "5. Access Token" --> SpringBoot
SpringBoot -- "6. User Info Request" --> Kakao
Kakao -- "7. User Profile" --> SpringBoot
SpringBoot -- "8. Issue JWT" --> Client

Client -- "Image Upload (JWT)" --> SpringBoot
SpringBoot -- "AWS SDK (Credentials)" --> S3
SpringBoot -- "JDBC" --> RDS
SpringBoot -- "HTTP POST (Image Location)" --> FastAPI
FastAPI -- "AWS SDK" --> S3[Fetch Image]
FastAPI -- "REST API Call" --> GoogleAI
GoogleAI -- "Analysis Result (JSON)" --> FastAPI
FastAPI -- "Generate Vector" --> FastAPI
FastAPI -- "Analysis Result + Vector (JSON)" --> SpringBoot
SpringBoot -- "Store Vector" --> VectorDB
SpringBoot -- "JDBC" --> RDS[Update Metadata]
SpringBoot -- "HTTP 200 OK" --> Client

Client -- "Recommendation Request (Image ID, JWT)" --> SpringBoot
SpringBoot -- "Query by ID" --> VectorDB
SpringBoot -- "k-NN Search" --> VectorDB
VectorDB -- "List of similar Image IDs" --> SpringBoot
SpringBoot -- "JDBC (Batch Fetch)" --> RDS[Hydrate Metadata]
SpringBoot -- "JSON Response" --> Client