Serverless Cold Start Calculator

Estimate cold start frequency and its effect on average latency.

About Serverless Cold Start Calculator

Cold start frequency depends on how invocations space out relative to the idle timeout, so sparse traffic suffers most. At high invocation rates containers stay warm and the penalty becomes negligible. Serverless is least suited to low-traffic latency-sensitive endpoints, which is precisely the case where its cost advantage looks most attractive.

Formula

Serverless Cold Start

Average latency = warm time + cold start share × cold start duration

idle timeout: How long a container is kept warm after an invocation
provisioned concurrency: Pre-warmed instances that eliminate most cold starts

Worked example

With the default values below, Serverless Cold Start Calculator returns Average Latency of 62.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Invocations per minuteminimum 0: 40
Cold start durationminimum 0 ms: 800 ms
Warm execution timeminimum 0.1 ms: 60 ms
Container idle timeoutminimum 0.1 min: 10 min
Provisioned concurrencyminimum 0: 0

Results

Average Latency: 62.00 ms
Share of Invocations Cold: 0.250%
Cold Starts per Hour: 6.00
Latency Penalty From Cold Starts: 2.00 ms
Recommendation: Cold start impact is modest at this traffic level

Step by step

1Values used
2Serverless Cold Start
3Average Latency= 62.00 ms
4Share of Invocations Cold= 0.250
5Cold Starts per Hour= 6.00
6Latency Penalty From Cold Starts= 2.00 ms
7Recommendation= Cold start impact is modest at this traffic level

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Serverless Cold Start calculated?

Average latency = warm time + cold start share × cold start duration Cold start frequency depends on how invocations space out relative to the idle timeout, so sparse traffic suffers most. At high invocation rates containers stay warm and the penalty becomes negligible.

Why does Serverless Cold Start matter?

Serverless is least suited to low-traffic latency-sensitive endpoints, which is precisely the case where its cost advantage looks most attractive.

What values do I need to enter?

This calculator takes 5 inputs: Invocations per minute, Cold start duration, Warm execution time, Container idle timeout, Provisioned concurrency. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.