index.js

const { ApolloServer, gql, Connector } = require("apollo-server");

const users = [{ id: 1, firstName: "James" }];

class UserConnector {
  getById(id) {
    return users.find(user => user.id == id);
  }
}

let votes = 0;

const server = new ApolloServer({
  typeDefs: gql`
    type Query {
      users: [User]
      foo: Foo
      votes: Int
    }

    type UpVoteReponse @mutationResponse {
      votes: Int
    }

    type Mutation {
      upvote: UpVoteReponse
    }

    type Foo {
      id: ID! @unique
    }

    type User @node {
      firstName: String
    }
  `,
  resolvers: {
    Query: {
      users: () => users,
      foo: () => ({ id: 1 }),
      votes: () => votes,
    },
    Mutation: {
      upvote: () => {
        votes++;
        return { votes };
      },
    },
  },
  context: async ({ request }) => ({
    connectors: { User: new UserConnector() },
  }),
});

server.listen();