Upgrading to CDK v2 solved it (https://docs.aws.amazon.com/cdk/v2/guide/migrating-v2.html)

The Node.js 18 Lambda runtime is preloaded with the AWS SDK for JS v3.

The earlier runtimes have the SDK v2.

Of course you can still use the SDK v2 with the Node.js 18 runtime. You just need to package the clients as dependencies with your Lambda code.

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The v2 SDK's aws-sdk package (preloaded on the 14.x, 16.x Lambda Node.js runtimes) contains every client. The v3 service clients (preloaded on 18.x) are modularised in separate @aws-sdk/client-[something] packages. Here's a v3 sample import for getting an S3 object:

// v3
import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3"

See the Getting Started guide in the SDK v3 docs.

you can see Deploy Node.js Lambda functions with .zip file archives for details: Runtime dependencies in Node.js: > Lambda periodically updates the SDK libraries in the Node.js runtime to include the latest features and security upgrades. Lambda also applies security patches and updates to the other libraries included in the runtime. To have full control of the dependencies in your package, you can add your preferred version of any runtime-included dependency to your deployment package. For example, if you want to use a particular version of the SDK for JavaScript, you can include it in your .zip file as a dependency. For more information on adding runtime-included dependencies to your .zip file, see Dependency search path and runtime-included libraries. Dependency search path and runtime-included libraries : > The Node.js runtime includes a number of common libraries, as well as a version of the AWS SDK for JavaScript. If you want to use a different version of a runtime-included library, you can do this by bundling it with your function or by adding it as a dependency in your deployment package .... > By default, the first location the runtime searches is the directory into which your .zip deployment package is decompressed and mounted (/var/task). If you include a version of a runtime-included library in your deployment package, this version will take precedence over the version included in the runtime >When you add a dependency to a layer, Lambda extracts this to /opt/nodejs/nodexx/node_modules where nodexx represents the version of the runtime you are using. In the search path, this directory has precedence over the directory containing the runtime-included libraries (/var/lang/lib/node_modules). Libraries in function layers therefore have precedence over versions included in the runtime. So you have three choices： 1. Use the original aws sdk js v3 sdk from AWS Lambda Nodejs runtime, and do not include any content of aws sdk js v3 sdk in your own zip package 2. Use your preferred SDK version and include it in the zip package 2. Use your preferred SDK version by use layer,so your preferred SDK version has precedence over the directory containing the runtime-included libraries