Estimate API response times (P50/P90/P99) based on model choice, geographic region, and expected concurrency. Plan your UX patterns accordingly.
Simultaneous requests
For Claude Sonnet 4.5 in US East (Virginia), expect median response times of 1.80s (P50), with 90% of requests completing within 2.70s (P90) and 99% within 4.50s (P99). These estimates assume typical network conditions and API health.
Moderate concurrency (10 concurrent) - add ~180ms buffer for queueing.
Near-Live - Responsive, brief wait acceptable
Brief waiting is acceptable with good UX. Use subtle loading indicators and optimistic UI updates.
Moderate concurrency (10 concurrent) - add ~180ms buffer for queueing.