With GraphQL, Facebook engineers promote a very good idea that there should be a clear boundary between the client and the server following common agreement. So, both parties can build and scale independently, with low coupling and high cohesion.

Isomorphic is not just about sharing code between the client and the server. It's beyond that. For example, with a GraphQL server, you can have the same data API endpoint serving both the web and multiple versions of mobile apps saving you lots of time and efforts.

By now, after completing this chapter, you should know how to write and execute GraphQL queries, via GraphiQL IDE, using Fetch API and directly by calling graphql(..) method on the server. You should become familiar with GraphQL type system and schema language. You should be able to create custom GraphQL schema backed by an SQL data store and using a Sequelize ORM and GraphQL JavaScript reference library. Finally, you should have an idea how to optimize your schema to work well...