Define performance SLIs (e.g., p95 latency) and monitor them continuously. Add profiling/tracing for slow endpoints, use load tests for critical flows, and set budgets/alerts so regressions are caught early. Feature flags can help you roll back quickly if needed.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "how-do-you-prevent-performance-regressions-in-a-"
function explain() {
// Start from the core idea:
// Define performance SLIs (e.g., p95 latency) and monitor them continuously. Add profiling/t
}