Performance Budgets for APIs

Performance budgets for APIs are predefined limits on key metrics—like latency, payload size, or CPU usage—that ensure consistent performance and prevent regressions as systems scale.

When to Use

Set API performance budgets during system design or release phases to catch performance issues early.

Use them when you need to maintain SLA guarantees or ensure new features don’t slow down endpoints.

Example

A team might define: “API response time ≤ 250ms for 95% of requests.”

If a new update violates this, alerts trigger or deployment halts until fixed.

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Why Is It Important

Budgets enforce predictable performance. They help teams build reliable APIs that scale smoothly, protecting user experience and system health.

Interview Tips

Be ready to discuss metrics (latency, throughput, CPU) and tools like rate limiters, monitoring dashboards, or load testing. Explain trade-offs confidently.

Trade-offs

Strict budgets improve reliability but may slow feature delivery. Looser budgets increase flexibility but risk performance drift.

Pitfalls

Avoid arbitrary limits or ignoring context (e.g., network variance). Update budgets regularly as your system and traffic evolve.

For deeper learning, explore Grokking the System Design Interview and Grokking Database Fundamentals for Tech Interviews.