How to Fix AWS Lambda Error: Cannot find module ‘aws-sdk’

Quick Diagnosis

  • ✓ Did you recently upgrade your AWS Lambda function’s runtime to Node.js 18.x or Node.js 20.x?
  • ✓ Does your function immediately fail at startup with a Runtime.ImportModuleError?
  • ✓ Is your Lambda handler using the legacy import syntax const AWS = require('aws-sdk')?

Environment

The AWS SDK loader resolves dependencies serverless-side during container initialization, executing across environments including AWS Lambda Serverless Functions, Cloudflare Workers edge runtimes, Custom Node.js container environments, and Webpack module bundle configurations.

Lambda Runtime Target Bundled Dependencies Scope Import Statement Path Lambda Invocation Result
Node.js 16.x or older None (Relies on pre-installed SDK) const AWS = require('aws-sdk') Success (Legacy SDK v2 pre-installed)
Node.js 18.x or 20.x None (Relies on pre-installed SDK) const AWS = require('aws-sdk') Failed (Error: Cannot find module ‘aws-sdk’)
Node.js 18.x or 20.x Bundled aws-sdk v2 (in zip package) const AWS = require('aws-sdk') Success (Resolves locally bundled legacy SDK)
Node.js 18.x or 20.x None (Relies on pre-installed SDK) import { S3Client } from '@aws-sdk/client-s3' Success (Uses pre-installed SDK v3)

Minimal Repro

Under AWS Lambda’s execution environment lifecycle, serverless containers are initialized using pre-packaged runtime image configurations. To reduce the default runtime container footprint and encourage modern coding practices, AWS runtimes beginning with Node.js 18.x removed the pre-installed monolithic AWS SDK for JavaScript v2 (aws-sdk). The runtime now bundles the modular AWS SDK for JavaScript v3 (@aws-sdk/*) by default. If your application codebase contains legacy import statements (const AWS = require('aws-sdk')) and you deploy to a Node.js 18+ runtime without bundling node_modules inside the deployment zip archive, the Node compiler fails to resolve the reference. The bootstrap process aborts immediately, throwing a Runtime.ImportModuleError containing the Error: Cannot find module 'aws-sdk' exception. Migrating imports to use the @aws-sdk client namespaces satisfies the runtime checker, or bundling the legacy package directly provides backwards compatibility.

// CRASH: Importing legacy v2 SDK on Node.js 18+ runtime
const AWS = require('aws-sdk');
const s3 = new AWS.S3();

exports.handler = async (event) => {
  const data = await s3.listBuckets().promise();
  return data;
};
{
  "errorType": "Runtime.ImportModuleError",
  "errorMessage": "Error: Cannot find module 'aws-sdk'\nRequire stack:\n/var/task/index.js",
  "trace": [
    "Runtime.ImportModuleError: Error: Cannot find module 'aws-sdk'",
    "Require stack:",
    "/var/task/index.js",
    "    at _loadUserApp (/var/runtime/UserFunction.js:221:12)",
    "    at Object.module.exports.load (/var/runtime/UserFunction.js:246:17)"
  ]
}

Resolution

When resolving missing SDK module errors in AWS Lambda, developers can choose between two main structural options depending on whether they can refactor their application code.

If you are updating your application or creating new functions, refactoring to the pre-installed AWS SDK for JavaScript v3 is applicable. This configuration reduces deployment zip sizes and leverages pre-installed runtime dependencies.

  1. Identify the modular package clients you require (e.g., @aws-sdk/client-s3).
  2. Replace monolithic imports with modular import paths.
  3. Instantiate specific clients directly (e.g., S3Client).
  4. Execute commands using client .send() method structures.
// Correct: Import modular client from pre-installed runtime dependencies
import { S3Client, ListBucketsCommand } from '@aws-sdk/client-s3';

// Instantiate Client
const s3Client = new S3Client({ region: process.env.AWS_REGION });

export const handler = async (event) => {
  try {
    // Construct modular client commands
    const command = new ListBucketsCommand({});
    const response = await s3Client.send(command);
    
    return {
      statusCode: 200,
      body: JSON.stringify({ buckets: response.Buckets })
    };
  } catch (err) {
    return {
      statusCode: 500,
      body: JSON.stringify({ error: err.message })
    };
  }
};

Option B: Bundle aws-sdk v2 Locally in the Deployment Package

If you manage large legacy codebases where refactoring the SDK calls is cost-prohibitive, bundling the aws-sdk library inside your deployment bundle is applicable. This restores legacy compatibility on Node 18+ runtimes.

  1. Add the legacy package to your dependencies: 
    npm install aws-sdk
  2. Package the node_modules directory containing aws-sdk inside your deployment zip archive before uploading to AWS.

When This Fix Won’t Work

If you deploy using custom Lambda Layers that explicitly delete or intercept local node_modules folders, runtime import calls for bundled packages can still fail. Verify Layer configurations before bundling legacy files.

Operational Runbook

Case 1: Node.js 18+ Upgrades

  1. Search codebase for instances of require('aws-sdk') or import AWS from 'aws-sdk'.
  2. Replace references with modular v3 packages.

Case 2: Legacy Deployments

  1. Install aws-sdk using package managers.
  2. Build zip packages including dependency files.

Rollback Strategy

To roll back this change, restore the previous SDK import references by replacing modular client instantiations with monolithic require('aws-sdk') constructor definitions, add the aws-sdk v2 library back to your local package.json dependencies checklist, and ensure the deployment package compiler bundles the node_modules directory.

Verification

  • AWS Lambda handler invocations complete returning HTTP 200 responses containing expected API data.
  • Serverless execution logs contain zero Runtime.ImportModuleError missing package messages.
  • Modular client instance requests execute successfully returning valid query results.

Error Trigger Point Lifecycle

Start Lambda container execution ➔ Load server handler file ➔ Evaluate require or import statements [ERROR OCCURS HERE] ➔ Initialize client resources ➔ Process client requests ➔ Return handler response

References