Cloud Infrastructure
Lambda Cold Start Estimator
Enter Lambda runtime, memory allocation, and deployment package size to estimate cold start duration range and cold start probability at your traffic level.
Calculations run locally in your browserTool
Example — Representative default scenario — memory MB 1024 · cold start ms 380 · requests per min 1200.
Est. cold start
165 ms
Node.js 20 at 1024MB
Cold start frequency
27.8%
at 5 RPS
P99 impact
~46 ms
on p99 latency
Mitigation
Provisioned concurrency
About this tool
Lambda Cold Start Estimator
The Lambda Cold Start Estimator computes cold start duration range by runtime and memory, cold start probability from traffic patterns, and provisioned concurrency break-even.
• Estimate cold start impact before choosing between Java and Node.js for a latency-sensitive function
• Calculate whether provisioned concurrency ROI is positive at a given RPS
• Understand how memory allocation affects cold start duration
• Model cold start probability for a function with variable traffic patterns
Next step
Continue with Utility Matrix tools for the next decision in this workflow.
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FAQ
What does this tool tell you?
The Lambda Cold Start Estimator computes cold start duration range by runtime and memory, cold start probability from traffic patterns, and provisioned concurrency break-even.
What affects the result most?
Lambda cold start duration by runtime: Java 11 800-3000ms, Python 3.11 100-400ms, Node.js 20 50-300ms, Go 50-150ms. Memory allocation impact: more memory = more CPU = faster initialization — 512MB vs 128MB cuts cold start by ~40%. VPC cold start penalty: adds 200-400ms historically, resolved in 2019 via Hyperplane ENI — no longer a factor.
How should I use the result?
The calculation is deterministic — the same inputs always produce the same output — so the most useful workflow is to vary one input at a time and see which factor moves the result most. That tells you where to focus your attention before committing to a decision.