Define the backend responsibilities
API development.
Database design.
Authentication.
Business logic.
Third-party integrations.
Background jobs.
Hosting or deployment.
Monitoring.
Ask about architecture
The technology choice matters, but the developer should also be able to explain how data, services and dependencies fit together.
Protect infrastructure ownership
Cloud accounts, repositories, databases and production credentials should remain under clear business control.
Backend work is difficult to judge from screenshots.Ask for comparable systems, architecture decisions and examples of how the developer handles reliability and maintenance.
Use functional milestones
Break development into working endpoints, integrations or system components that can be tested before the entire build is complete.