Database per service

Each service owns its data and no other service reads its tables directly; the others go through its API or its events.

A shared database couples services more tightly than any API: one schema change breaks three teams. With a database per service, each team can change its schema freely. The price is that joins across services are gone: a report needs a read model built from events (CQRS), and a change across services needs a saga.

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Related terms

Microservices: An architecture where a system is built from small, separately deployed services, each owning its data and talking to the others over the network.
Saga pattern: A business process across several services run as a chain of local transactions, with a compensating action to undo each step if a later one fails.
CQRS (Command Query Responsibility Segregation): Splitting a system into a write side that changes data and a separate read side shaped for queries, kept in sync by events.

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