Planning a multi-system cloud migration

[Fixture] Architecture and delivery plan for moving several interdependent systems to the cloud without a big-bang cutover.

Context

[Fixture] A logistics business running five interconnected services.

The systems shared a database and deployment schedule, so no single service could move without risking the others.

Architect responsible for the target design and the migration plan.

Documented the real dependencies between services and drew the target architecture.

Split the migration into stages, each with a rollback point.

Introduced integration contracts so services could move independently.

The migration ran in stages with no unplanned downtime, and the services can now be deployed independently.