https://apoorv.blog/lambda-layers-cdk/

discount.js

exports.discountForProduct = (productId) => {

    const products = [
        {
            productId: '1',
            discount: '10%'
        },
        {
            productId: '2',
            discount: '20%'
        },
        {
            productId: '3',
            discount: '30%'
        }
    ]

    const item = products.find(element => element.productId === productId)

    return item.discount
}

index.js

const uuid = require('uuid/v4')
const { discountForProduct } = require('./discount')

exports.handler = async(event) => {

    const { productId } = event.queryStringParameters

    return {
        statusCode: 200,
        body: JSON.stringify({ 
            transactionId: uuid(), 
            discount: discountForProduct(productId),
            message: 'from lambda one'
        })
    }
}

lambda-fns.ts

new Function(this, 'oneFn', { 
  runtime: Runtime.NODEJS_14_X,
  code: Code.fromAsset(`${__dirname}/../lambda-fns/one/deployment.zip`),
  handler: 'index.handler',
  layers: [latestLayer]
})

new Function(this, 'twoFn', { 
  runtime: Runtime.NODEJS_14_X,
  code: Code.fromAsset(`${__dirname}/../lambda-fns/two/deployment.zip`),
  handler: 'index.handler',
  layers: [latestLayer]
})

latestLayer.ts

const latestLayer = LayerVersion.fromLayerVersionAttributes(this, 'latestLayer', {
  compatibleRuntimes: [Runtime.NODEJS_14_X],
  layerVersionArn
})

layer.ts

const layer = new LayerVersion(this, 'uuidLayer', {
  code: Code.fromAsset(`${__dirname}/../lambda-fns/layer/deployment.zip`),
  compatibleRuntimes: [ Runtime.NODEJS_14_X],
  description: 'uuid package and discount for product'
})

layer.addPermission('layerPermission', {
  accountId: account
})

new CfnOutput(this, 'layerVersionArn', {
  value: layer.layerVersionArn
})