Client (Auth: Bearer <access_token>)
   └─1. POST /v1/datastores
       └─▶ API Gateway (validate token, rate-limit)
           └─▶ Ingestion Service
               └─▶ Schema Registry
                   └─▶ S3 Storage (profiles, interactions, content)

  Client (Auth: Bearer <access_token>)
   └─2. POST /v1/datastores/{ds}/train
       └─▶ API Gateway (validate token, rate-limit)
           └─▶ Training Orchestrator
               └─▶ Model Registry
                   └─▶ S3 Storage (model checkpoints)

  Client (Auth: Bearer <access_token>)
   └─3a. GET /v1/datastores/{ds}/recommendations/user
       └─▶ API Gateway (validate token, rate-limit, check scopes)
           └─▶ Inference Service
               └─▶ Model Registry
                   └─▶ Response: Top‑K Items for User

  Client (Auth: Bearer <access_token>)
   └─3b. GET /v1/datastores/{ds}/recommendations/session
       └─▶ API Gateway (validate token, rate-limit, check scopes)
           └─▶ Inference Service
               └─▶ Model Registry
                   └─▶ Response: Top‑K Items for Session