Your question is Server-Side Validation. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
how will you do server side validation before hitting the application?
Asked in the F2F stage.
Explain where validation belongs, what checks run before application logic, how invalid requests are rejected, and how the design handles authentication, authorization, malformed input, abuse, observability, and downstream failures.
Address the validation flow, API boundaries, schema and business-rule checks, security controls, failure responses, rollout, and testing strategy. Keep the design practical and explain the tradeoffs between gateway, service, and application-layer validation.