AWS Lambda preview runtimes let serverless teams test Node.js 26 and Python 3.15 before GA. Here is how to benchmark them safely, without risking production.
Key takeaways
- AWS introduced public preview runtimes on Lambda, starting with Node.js 26 and Python 3.15, a departure from its historical general-availability-only policy.
- AWS states these preview runtimes are not covered by the Lambda SLA or technical support and should not be used for production, because breaking changes are still possible before the stable release.
- Both languages are expected to reach stable upstream releases around October 2026, with Lambda GA targeted within about two months after each.
- Van Data Team's recommendation: use preview runtimes to test dependencies and measure cold starts in isolated, non-production accounts, and treat every finding as input to a planned GA upgrade.
📖 Read the full guide on Van Data Team → Lambda Preview Runtimes: What AWS's Shift Means
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