Single endpoint architecture in GraphQL - Mini Project: Build & Apply

Build a Simple GraphQL Single Endpoint

📖 Scenario: You are creating a simple GraphQL API for a bookstore. The API will have a single endpoint that allows clients to query for books and authors.

🎯 Goal: Build a GraphQL schema with a single endpoint that supports querying books and authors with their details.

📋 What You'll Learn

Create a GraphQL type for Book with fields id, title, and authorId.

Create a GraphQL type for Author with fields id and name.

Create a root Query type with fields books and authors that return lists of Book and Author respectively.

Use a single GraphQL endpoint to serve all queries.

💡 Why This Matters

🌍 Real World

Single endpoint GraphQL APIs are used in modern web and mobile apps to fetch exactly the data needed in one request.

💼 Career

Understanding how to design GraphQL schemas and resolvers is essential for backend developers working with APIs.

1

Define Book and Author Types

Create GraphQL types called Book and Author. Book should have fields id (ID!), title (String!), and authorId (ID!). Author should have fields id (ID!) and name (String!).

GraphQL

# Define the Book and Author types
# Your code here

Hint

Use type keyword to define GraphQL object types with their fields and types.

2

Create Root Query Type

Create a root Query type with two fields: books and authors. Both fields should return a list of their respective types: [Book] and [Author].

GraphQL

type Book {
  id: ID!
  title: String!
  authorId: ID!
}

type Author {
  id: ID!
  name: String!
}

# Define the Query type with books and authors fields
# Your code here

Hint

The root Query type defines the entry points for queries. Use square brackets [] to indicate lists.

3

Add Sample Data

Create two arrays called books and authors with sample data. books should have two objects with fields id, title, and authorId. authors should have two objects with fields id and name.

GraphQL

type Book {
  id: ID!
  title: String!
  authorId: ID!
}

type Author {
  id: ID!
  name: String!
}

type Query {
  books: [Book]
  authors: [Author]
}

# Add sample data arrays for books and authors
# Your code here

Hint

Use JavaScript arrays of objects to hold sample data matching the GraphQL types.

4

Add Resolvers for Query Fields

Create a resolvers object with a Query field. Inside Query, add two functions: books and authors. Each function should return the corresponding array: books or authors.

GraphQL

type Book {
  id: ID!
  title: String!
  authorId: ID!
}

type Author {
  id: ID!
  name: String!
}

type Query {
  books: [Book]
  authors: [Author]
}

const books = [
  { id: "1", title: "1984", authorId: "1" },
  { id: "2", title: "Animal Farm", authorId: "1" }
];

const authors = [
  { id: "1", name: "George Orwell" },
  { id: "2", name: "Aldous Huxley" }
];

# Add resolvers object with Query field returning books and authors
# Your code here

Hint

Resolvers connect the schema fields to the data. Use arrow functions returning the sample arrays.

Practice

1. What is the main advantage of using a single endpoint architecture in GraphQL?

easy

A. It increases the complexity of client requests.

B. It requires multiple URLs for different data types.

C. It limits the flexibility of data fetching.

D. It allows all data queries to be sent to one URL.

Solution

1. Step 1: Understand the concept of single endpoint

   Single endpoint architecture means all queries go through one URL.

2. Step 2: Compare options with this concept

   Only It allows all data queries to be sent to one URL. states this clearly; others contradict the concept.

3. Final Answer:

   It allows all data queries to be sent to one URL. -> Option D

4. Quick Check:

   Single endpoint = one URL [OK]

Hint: Single endpoint means one URL for all queries [OK]

Common Mistakes:

• Thinking multiple URLs are needed
• Confusing flexibility with complexity
• Assuming single endpoint limits data fetching

2. Which of the following is the correct way to define a GraphQL endpoint URL for single endpoint architecture?

easy

A. /api/users, /api/posts

B. /data/users

C. /graphql

D. /api/v1/data

Solution

1. Step 1: Identify typical single endpoint URL

   GraphQL commonly uses a single endpoint like '/graphql' for all queries.

2. Step 2: Check other options

   Options A, C, and D suggest multiple or REST-style URLs, not single endpoint.

3. Final Answer:

   /graphql -> Option C

4. Quick Check:

   Single endpoint URL = /graphql [OK]

Hint: Single endpoint usually named '/graphql' [OK]

Common Mistakes:

• Choosing multiple URLs instead of one
• Confusing REST endpoints with GraphQL
• Ignoring standard naming conventions

3. Given the GraphQL query sent to a single endpoint /graphql:

{ user(id: "1") { name email } }

What will the server return?

medium

A. 404 Not Found

B. { "data": { "user": { "name": "Alice", "email": "[e-mail]" } } }

C. { "error": "Multiple endpoints required" }

D. { "data": { "users": [] } }

Solution

1. Step 1: Understand the query and endpoint

   The query requests user data by id from the single endpoint '/graphql'.

2. Step 2: Predict server response

   The server returns the requested user data in JSON format under 'data'. { "data": { "user": { "name": "Alice", "email": "[e-mail]" } } } matches this.

3. Final Answer:

   { "data": { "user": { "name": "Alice", "email": "[e-mail]" } } } -> Option B

4. Quick Check:

   Query returns requested user data [OK]

Hint: Single endpoint returns data in 'data' field JSON [OK]

Common Mistakes:

• Expecting HTTP 404 for valid query
• Thinking multiple endpoints needed
• Confusing error format with data response

4. A developer tries to send two different queries to separate URLs /api/users and /api/posts but gets errors. What is the likely problem in a GraphQL single endpoint setup?

medium

A. GraphQL requires all queries to go through a single endpoint URL.

B. The URLs are correct; the error is due to query syntax.

C. Multiple endpoints are allowed; the server is down.

D. The client must send queries via GET, not POST.

Solution

1. Step 1: Identify the architecture requirement

   GraphQL single endpoint architecture requires all queries to use one URL.

2. Step 2: Analyze the error cause

   Using multiple URLs breaks this rule, causing errors. GraphQL requires all queries to go through a single endpoint URL. explains this correctly.

3. Final Answer:

   GraphQL requires all queries to go through a single endpoint URL. -> Option A

4. Quick Check:

   Single endpoint means one URL [OK]

Hint: All GraphQL queries use one URL [OK]

Common Mistakes:

• Assuming multiple endpoints are allowed
• Blaming query syntax without checking URL
• Confusing HTTP methods with endpoint issues

5. How does single endpoint architecture improve backend management in a GraphQL API?

hard

A. It centralizes all data fetching through one URL, simplifying routing and security.

B. It requires separate servers for each data type, increasing complexity.

C. It forces clients to send multiple requests to different URLs.

D. It limits the types of queries clients can make.

Solution

1. Step 1: Understand backend management benefits

   Single endpoint centralizes requests, making routing and security easier to manage.

2. Step 2: Evaluate options

   It centralizes all data fetching through one URL, simplifying routing and security. correctly states this benefit; others describe drawbacks or incorrect facts.

3. Final Answer:

   It centralizes all data fetching through one URL, simplifying routing and security. -> Option A

4. Quick Check:

   Centralized endpoint = simpler backend [OK]

Hint: One URL centralizes backend tasks [OK]

Common Mistakes:

• Thinking multiple servers are needed
• Believing clients must send many requests
• Assuming query types are limited