AWS Lambda Public Preview Runtimes Introduced for Node.js 26 and Python 3.15

AWS Lambda has announced the introduction of managed runtimes in public preview for Node.js 26 and Python 3.15, according to the official AWS What's New changelog. This marks a shift in how Lambda runtimes are released, as previously they were launched directly as general availability (GA) versions. The public preview allows users to test workloads and provide feedback before the runtimes reach GA, during which breaking changes are still possible. This approach also gives third-party observability providers, infrastructure-as-code tools, and deployment frameworks an opportunity to validate compatibility ahead of GA. It is important to note that these preview runtimes are not covered by the Lambda SLA or AWS Technical Support plans and are not recommended for production workloads.

Operators should carefully evaluate whether their development or testing environments can accommodate potential breaking changes during the preview period. Additionally, they should ensure that any automation tools, deployment pipelines, or observability systems they rely on are compatible with these preview runtimes. Since the runtime identifiers remain consistent between preview and GA, functions using these runtimes will automatically transition to GA without requiring manual intervention, but operators should still monitor for any runtime-specific updates or issues that arise during the preview phase.