Serverless Cold Start Rate Calculator
Compute serverless cold start rate and weighted latency penalty from invocation telemetry to monitor reliability and performance SLO risk.
This calculator summarizes observed behavior and should be combined with percentile latency monitoring for full performance diagnostics.
Examples
- Cold starts 4,500, total invocations 250,000, cold start latency 450 ms, target 2% => Cold start rate: 1.80%. Weighted latency penalty: 8.10 ms per invocation. Target: 2.00%. Gap: −0.20% vs target.
- Cold starts 2,000, total invocations 50,000, optional fields blank => Cold start rate: 4.00%. Weighted latency penalty: 16.00 ms per invocation. Target: 2.00%. Gap: +2.00% vs target.
FAQ
What should count as a cold start?
Use your platform's initialization telemetry and count invocations that required runtime startup before handling the request.
Why show weighted latency penalty?
Weighted penalty translates the cold start ratio into average end-user delay, making the operational impact easier to compare with latency objectives.
How often should I recalculate this metric?
Track it per deployment and at least daily in production because traffic shape, memory settings, and release changes can move cold start behavior quickly.
Additional Information
- Cold start rate is unitless but reported as a percent with two decimals.
- If cold start latency is left blank, a default value of 400.00 ms is used.
- If target rate is left blank, a default threshold of 2.00% is used for benchmarking.