GraphQL

Let's have a look at some interesting things about #graphql. As a #backend developer, you may already be familiar with GraphQL and its basics. However, there are some lesser-known features and advanced techniques that you may find interesting and useful, and why not start using them․

let's talk about just some of them.

• #CustomDirectives

One of the most powerful and flexible features of #GrapQL is its support for custom directives. Directives are annotations that can be added to fields, arguments, and even entire operations in a GraphQL query. They allow you to add custom behavior to your schema without having to modify the underlying data model.

For example, you could define a custom @auth directive that checks whether a user is authorized to access a particular field. Or you could define a @cache directive that tells the server to cache the result of a query for a certain amount of time.

To define a custom directive in GraphQL, you simply add a new directive definition to your schema:

directive @auth(roles: [String]) on FIELD_DEFINITIO
directive @cache(seconds: Int) on FIELD_DEFINITION        

Then, you can add these directives to your query or mutation

query {
  suites @auth(roles: ["admin", "editor"]) {
    id
    title
    orgId
  }
}


query {
  projects @cache(seconds: 60) {
    id
    title
    suiteId
  }
}        

• #BatchedResolvers

In some cases, you may need to resolve multiple fields in a GraphQL query that are related to each other. For example, you might have a query that fetches a user's profile and their list of posts. Instead of making separate API calls for each field, you can use batched resolvers to fetch all the data in a single request.

Batched resolvers are resolvers that can return an array of promises instead of a single promise. GraphQL will automatically wait for all the promises to resolve before returning the response to the client.

Here's an example of how you might implement a batched resolver for a user's profile and posts

const resolvers = 
  User: {
    profileAndPosts: async (user, _, { dataSources }) => {
      const [profile, posts] = await Promise.all([
        dataSources.profileAPI.getProfile(user.id),
        dataSources.postAPI.getPostsByUser(user.id),
      ]);
      return { profile, posts };
    },
  },
};        

Then, you can use this resolver in your schema

type User 
  id: ID!
  name: String!
  profileAndPosts: ProfileAndPosts!
}


type ProfileAndPosts {
  profile: Profile!
  posts: [Post!]!
}


type Query {
  user(id: ID!): User
}        

Now, when you query for a user and their profile and posts GraphQL will automatically batch the requests for the profile and posts into a single API call.

• #Federation

As a backend developer, you can work on large microservice-based architectures where each service has its own database and API. GraphQL federation allows you to build a distributed API by combining multiple GraphQL services into a single schema. Each service is responsible for a specific domain or data source, and the federation layer acts as a gateway that routes requests to the appropriate service.

By using federation, you can expose a unified API to your clients without having to merge all your services into a single monolithic API. This can make it easier to manage and scale your backend architecture over time.

To use federation, you need to define a schema for each service that includes special @key directives that specify how entities in the schema are related to each other. Once you've defined your schemas, you can use a federation gateway to route requests to the appropriate service based on the @key directives.

In conclusion, these are a few of the features that graphql has, so #GraphQl is a powerful and flexible technology that offers many advanced features and techniques that can help you build better #APIs. By taking advantage of these features, you can make your backend architecture more scalable, performant, and maintainable over time.