Use aws-lambda types, it have types for most of the events.

Example handlers:

import { SQSHandler, SNSHandler, APIGatewayProxyHandler } from 'aws-lambda';

export const sqsHandler: SQSHandler = async (event, context) => {
  
}

export const snsHandler: SNSHandler = async (event, context) => {
}

export const apiV2Handler: APIGatewayProxyHandler = async (event, context) => {
  return {
    body: 'Response body',
    statusCode: 200
  }
}

Since November 2023 there is also LambdaFunctionURLHandler type in the @types/aws-lambda npm package. Here's the source on Github.

To get type checking in TypeScript use:

import { LambdaFunctionURLHandler } from 'aws-lambda';
export const handler: LambdaFunctionURLHandler = async (event) => {
  // handler code
}

You can also specify the type of the handler like this in JavaScript with JSDoc:

/** @type import('aws-lambda').LambdaFunctionURLHandler */
export const handler = async (event) => {
  // handler code
}

which especially useful if you are editing JS code in a type-aware code editor, but also uploading the Lambda code directly to AWS without transpiling.

The @types/aws-lambda package provides types for using TypeScript inside of an AWS Lambda function. For AWS Lambda functions invoked using API Gateway's Lambda Proxy integration type take the following steps:

Install the package

$ yarn add --dev @types/aws-lambda

Or if you prefer npm:

$ npm i --save-dev @types/aws-lambda

Then in your handler file:

import { APIGatewayProxyEvent, Context, APIGatewayProxyResult } from "aws-lambda"

export async function hello (event: APIGatewayProxyEvent, context: Context): Promise<APIGatewayProxyResult> {
  return {
    statusCode: 200,
    body: JSON.stringify({
      message: 'Hello world',
      input: event,
    })
  }
}