Load Testing

You might say

Before the event, simulate many real checkout users and show how latency, throughput, and error rate behave at the target load.

Load testing measures latency, throughput, and errors while a system handles a realistic level of load.Before an event, an isolated production-like environment can simulate browsing and checkout with synthetic or sanitized data. The team records response time, throughput, and failures, then compares them with predefined thresholds to decide what to improve. Load testing is not the same as pushing a system to its breaking point with stress testing, and it cannot promise zero production failures.
Load Testing
Further reading