webpack.config.js

const path = require('path');
const slsw = require('serverless-webpack');
const ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');
const nodeExternals = require('webpack-node-externals');
const TsconfigPathsPlugin = require('tsconfig-paths-webpack-plugin');

module.exports = {
  // `mode` will be set to `production` and comes with included optimizations
  // when building to be run on AWS or similar. 
  // https://webpack.js.org/configuration/mode/
  mode: slsw.lib.webpack.isLocal ? 'development' : 'production',

  // to determine what source maps to use per dev or prod
  // https://webpack.js.org/configuration/devtool/
  devtool: slsw.lib.webpack.isLocal ? 'source-map' : 'cheap-source-map',

  // the provided argument will be an object referencing functions as defined
  // in your `serverless.yml` .
  // https://webpack.js.org/concepts/entry-points/
  entry: slsw.lib.entries,

  target: 'node',

  resolve: {
    extensions: ['.js', '.ts'],
    plugins: [new TsconfigPathsPlugin()]
  },

  // Where the bundled files will be output. Not strictly necessary with 
  // Serverless Webpack.
  // https://webpack.js.org/configuration/output/
  output: {
    libraryTarget: 'commonjs2',
    path: path.join(__dirname, '.webpack'),
    filename: '[name].js',
  },

  externals: [nodeExternals()],
  module: {
    // Instruct Webpack to use the `ts-loader` for any TypeScript files, else it
    // won't know what to do with them.
    rules: [
        {
            test: /\.ts$/,
            exclude: /node_modules/,
            loader: 'ts-loader',
            exclude: [
              [
                path.resolve(__dirname, '.webpack'),
                path.resolve(__dirname, '.serverless'),
              ],
            ],
            // And here we have options for ts-loader
            // https://www.npmjs.com/package/ts-loader#options
            options: {
              // Disable type checking, this will lead to improved build times
              transpileOnly: true,
              // Enable file caching, can be quite useful when running offline
              experimentalFileCaching: true,
            },
        },
    ]
  },
  // We still want type checking, just without the burden on build performance, 
  // so we use a plugin to take care of it on another thread.
  plugins: [new ForkTsCheckerWebpackPlugin()]
};