Runs the same query on both designs at once.
Database per service
✓ Reporting hammers its own read-model. Checkout & Login DBs are untouched.
What just happened
- ▹A shared database is a hidden coupling: Reporting's heavy query locks the same tables checkout and login depend on.
- ▹Users feel it instantly — spinners freeze on flows that have nothing to do with reporting.
- ▹Database-per-service isolates the blast radius. Reporting reads its own read-model; user flows never notice.