
AWS SDK for JavaScript v3 significantly reduces Lambda cold start times compared to v2, with improvements ranging from over 100ms when using Lambda's provided SDK to over 400ms when bundled with esbuild, while also reducing function size.


<div><p>This article benchmarks AWS SDK for JavaScript v3 against v2, demonstrating significant Lambda cold start time improvements across common deployment scenarios.</p><ul><li>v3 reduces cold start times by >100ms with Lambda-provided SDK</li><li>v3 reduces cold start times by ~140ms with user-uploaded node_modules</li><li>v3 reduces cold start times by >400ms when bundled with esbuild</li><li>v3 has smaller bundle sizes due to modular architecture</li><li>Bundling with esbuild and using barebones clients with command objects provides optimal performance</li><li>v3 offers first-class TypeScript support and improved middleware stack</li><li>Recommendation: use v3 with barebones clients, bundled via esbuild or AWS CDK</li></ul><p>Migrating to AWS SDK for JavaScript v3 significantly improves Lambda cold start performance, especially when bundled and using command-based imports.</p></div>


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