A Netlify Lambda Function for that uses Apollo GraphQL

graphql.js

const { ApolloServer, gql } = require('apollo-server-lambda');
const MongoClient= require('mongodb/lib/mongo_client');

if (process.env.NODE_ENV !== 'production') {
  require('dotenv').load()
}

const DB_URI = process.env.DB_URI
const DB_NAME = process.env.DB_NAME

exports.handler = async function() {
  const client = await MongoClient.connect(DB_URI)
  const db = client.db(DB_NAME)
  const Posts = db.collection('posts')
  
  const typeDefs = gql`
    type Query {
      post: Post
      posts: [Post]
    }
    
    type Post {
      _id: String!
      title: String!
      content: String!
      comments: [Comment]
    }
  `;
  
  const resolvers = {
    Query: {
      post: async (root, { _id }) => {
        return await Posts.findOne(_id)
      },
      posts: async () => {
        return await Posts.find({}).toArray()
      }
    },
    
    Mutation: {
      createPost: async (root, args) => {
        const res = await Posts.insert(args)
        return await Posts.findOne({ _id: res.insertedIds[1] })
      }
    }
  };
  
  const server = new ApolloServer({
    typeDefs,
    resolvers,
  });
  
  const handler = server.createHandler();
  return handler(...arguments);
};