Problem Statement
How do you turn an HLD API into an LLD design the team can implement next sprint?
Explanation
Derive modules, interfaces, and data transfer objects. Pick patterns (e.g., Strategy, Adapter) to isolate variability. Define class responsibilities and contracts per SOLID.
Add sequence diagrams for critical flows, error handling, retries, and idempotency. Specify test seams and feature flags to release safely.
