Latency Percentile Calculator

Garbage collection pauses, resource contention, cold caches, network retries, connection pool exhaustion, or hitting slow database queries.

Under 5x is good. Under 10x is acceptable. Over 10x indicates serious tail latency issues that need investigation.

If your histogram shows two peaks, you likely have two code paths — cache hit vs miss, fast vs slow query, or primary vs fallback service.

Both. Server-side misses network latency. Client-side includes everything the user experiences. The gap between them reveals network issues.

With load balancing, a user making 10 API calls per page load has a ~10% chance of hitting a P99 response. At scale, tail latency always matters.

Set timeouts aggressively, use circuit breakers, pre-warm caches, reduce GC pressure, use connection pooling, and add request hedging.

Start with P95 < 200ms for APIs, P99 < 1s. Adjust based on your users' expectations and your system's baseline performance.

Yes, if the cache hit rate is high. But cache misses become your new P99. Consider pre-warming and background refresh to reduce cold cache latency.

Send a duplicate request after P95 latency. Cancel whichever finishes second. This dramatically reduces tail latency at the cost of ~5% extra load.

Warden measures response time on every check (every 30 seconds) and calculates P50, P95, and P99 over time. It alerts when percentiles exceed your thresholds.