Database per Service

Each service owns its database and no other service reads or writes it directly.

data

Detailed Description

Data ownership is one of the strongest service boundaries. A service API becomes the only allowed access path.

This enables independent evolution but pushes cross-service read needs into composition, projections, or events.

Visual Diagram

Data Ownership Model
  UserService    → [PostgreSQL db_users]
  OrderService   → [MongoDB   db_orders]
  ProductService → [Redis     db_products]
  SearchService  → [Elastic   db_search]

  ✗ OrderService cannot query db_users directly
  ✓ OrderService calls UserService API instead

Tradeoffs

Pros

Loose coupling, independent schema changes

Cons

Cross-service queries become harder

Examples: Microservices data ownership best practice