---
title: "Cold Start — Definition | FourSight Glossary"
url: https://foursight.cloud/glossary/cold-start
description: "The latency penalty incurred the first time a serverless function runs after a period of inactivity, while the runtime is being initialized. Can range f…"
lang: en
---

Back to glossary: https://foursight.cloud/glossary

Web & Networking

# Cold Start

The latency penalty incurred the first time a serverless function runs after a period of inactivity, while the runtime is being initialized. Can range from tens of milliseconds to several seconds.

Source

- AWS Lambda Operator Guide — Cold starts (https://docs.aws.amazon.com/lambda/latest/operatorguide/execution-environments.html)

Related guide: Monitoring AWS Lambda & API Gateway: https://foursight.cloud/guides/monitoring-aws-lambda-apis

## Related terms

HTTP Status Codes (2xx / 4xx / 5xx)

Three-digit response codes returned by HTTP servers.
https://foursight.cloud/glossary/http-status-codes

Timeout

The maximum time a client waits for a response before giving up.
https://foursight.cloud/glossary/timeout

DNS (Domain Name System)

The internet's address book — translates human-readable domain names like foursight.cloud into IP addresses…
https://foursight.cloud/glossary/dns

A Record

A DNS record that maps a hostname to an IPv4 address (e.g.
https://foursight.cloud/glossary/a-record

AAAA Record

Maps a hostname to an IPv6 address.
https://foursight.cloud/glossary/aaaa-record

CNAME Record

An alias DNS record that points one hostname to another (e.g.
https://foursight.cloud/glossary/cname-record

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