LLM Time-to-First-Token Latency Spike
warninglatencyUpdated Feb 12, 2026
High time-to-first-token from LLM providers indicates queuing, rate limiting, or model cold starts, causing user-perceived delays even when total generation time is acceptable.
Sources
Technologies:
How to detect:
Monitor gen_ai_server_time_to_first_token for values exceeding acceptable thresholds (e.g., >2 seconds). Compare against gen_ai_server_time_per_output_token to isolate startup latency from generation latency. Alert on sustained increases in TTFT across requests.
Recommended action:
Implement request warming or keep-alive patterns to reduce cold start delays. Monitor provider-specific TTFT SLAs and switch providers or models when thresholds are exceeded. Use streaming responses to show progress during long TTFT delays. Alert on TTFT regressions that impact user experience.