Introduction

GraphQL has revolutionized API development by offering flexible data fetching, type safety, and declarative queries. However, building a GraphQL API in Ruby on Rails comes with challenges, such as query optimization, security, and performance bottlenecks.

In this guide, we’ll explore:
✅ Advanced GraphQL implementation in Rails
✅ Optimizing performance with batching and caching
✅ Securing GraphQL APIs with authentication & authorization
✅ Handling complex queries and avoiding N+1 problems

By the end, you’ll be able to build scalable, production-ready GraphQL APIs in Rails. 🚀

1. Setting Up GraphQL in a Rails Application

To build a GraphQL API in Rails, we use the graphql-ruby gem:

📌 Install GraphQL in Rails
bundle add graphql
rails generate graphql:install

This creates:

  • app/graphql directory for schema, types, and mutations
  • GraphqlController to handle requests
📌 Define Your First GraphQL Type

Create a UserType to expose user data:

class Types::UserType < Types::BaseObject
field :id, ID, null: false
field :name, String, null: false
field :email, String, null: false
end
📌 Add Queries to Fetch Users

Modify QueryType to fetch users:

class Types::QueryType < Types::BaseObject
field :users, [Types::UserType], null: false

def users
User.all
end
end

Now, you can fetch users with:

query {
users {
id
name
email
}
}

2. Avoiding N+1 Queries with GraphQL

A common GraphQL pitfall is N+1 queries when fetching related records.

❌ Bad Example (Triggers Multiple Queries)
class Types::UserType < Types::BaseObject
field :posts, [Types::PostType], null: true

def posts
object.posts # Triggers N+1 query
end
end
✅ Solution: Use includes to Eager Load
def users
User.includes(:posts).all
end

This loads users and their posts in one query, avoiding performance issues.

✅ Optimize Further with batch-loader

The batch-loader gem eliminates N+1 issues:

class Types::UserType < Types::BaseObject
field :posts, [Types::PostType], null: true

def posts
BatchLoader::GraphQL.for(object.id).batch do |user_ids, loader|
Post.where(user_id: user_ids).each { |post| loader.call(post.user_id, post) }
end
end
end

Now, GraphQL efficiently batches and caches queries.

3. Implementing Authentication in GraphQL

APIs need authentication to restrict access. Use JWT with Devise:

📌 Generate JWT Authentication
bundle add devise
rails generate devise:install
rails generate devise User
📌 Secure GraphQL Queries with Current User

Modify context to include authentication:

class GraphqlController < ApplicationController
before_action :authenticate_user!

def execute
context = { current_user: current_user }
result = MyAppSchema.execute(params[:query], context: context)
render json: result
end
end
📌 Restrict Query Access
class Types::QueryType < Types::BaseObject
field :current_user, Types::UserType, null: true

def current_user
context[:current_user] # Only authenticated users can access
end
end

Now, clients must send a valid token to access user data.

4. Implementing Role-Based Authorization

Use Pundit for fine-grained authorization:

bundle add pundit
📌 Define Policies for Authorization
class UserPolicy < ApplicationPolicy
def update?
user.admin? || record == user
end
end
📌 Restrict Mutations Based on Role
class Mutations::UpdateUser < Mutations::BaseMutation
argument :id, ID, required: true
argument :name, String, required: false

field :user, Types::UserType, null: false

def resolve(id:, name:)
user = User.find(id)
raise GraphQL::ExecutionError, "Not authorized" unless UserPolicy.new(context[:current_user], user).update?

    user.update!(name: name)
    { user: user }
end
end

This ensures only authorized users can update profiles.

5. Optimizing GraphQL Performance

Large queries slow down responses. Use these techniques:

📌 Limit Query Depth

To prevent abusive queries, set max depth:

GraphQL::Schema.define do
max_depth 10
end
📌 Use Query Complexity Analysis

Limit expensive queries:

GraphQL::Schema.define do
default_max_page_size 50
max_complexity 200
end
📌 Implement Response Caching

Use graphql-cache gem to cache responses:

field :posts, [Types::PostType], null: true, cache: true

Now, frequently requested data is served faster.

Conclusion

GraphQL is powerful, but performance and security must be carefully managed. By:

✅ Optimizing queries to prevent N+1 issues
✅ Implementing authentication & authorization
✅ Limiting query complexity and depth
✅ Caching responses for better performance

You can build a scalable, production-ready GraphQL API in Rails. 🚀

Do you use GraphQL in your Rails projects? Let’s discuss in the comments!