Glossary
A way to run operations across several services when there is no shared transaction: every step has a compensating step.
As soon as an operation touches several services with their own databases, there is no common rollback. The saga pattern replaces it with business-level compensation: payment reversed, reservation released, order cancelled.
It is implemented either with an orchestrator that knows the steps, or event-driven, where each service reacts to the outcome of the previous one.