✅ A. Load Testing
Simulates a realistic volume of users or transactions (in this case, over 100,000 orders per day).
Helps verify whether the system can handle the expected load without performance degradation.
✅ D. Performance Testing
Measures response times, latency, and system efficiency under various conditions.
Helps identify bottlenecks in REST API processing, business logic execution, or database insert operations.
❌ Why not the others?
B. Unit Testing
→ Focuses on validating business logic at the code level, but does not test performance or scalability.

C. Stress Testing
→ Tests the system under extreme or breaking-point conditions (beyond expected load). It’s useful, but not as critical here as realistic load testing.

Ans = A and C