Single endpoint architecture in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

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

GraphQL uses a single endpoint for all queries and mutations. What is the primary benefit of this approach compared to REST APIs with multiple endpoints?

A It reduces the number of network requests by allowing clients to request exactly what they need in one call.

B It forces clients to download all data at once, improving performance.

C It requires clients to know all endpoints beforehand to fetch data.

D It limits the API to only support queries, not mutations.

💡 Hint

Think about how many requests a client needs to make to get data in REST vs GraphQL.

Using a single endpoint allows clients to specify exactly what data they want, reducing multiple network calls and improving efficiency.

❓ query_result

intermediate

What is the output of this GraphQL query using a single endpoint?

Given the schema with a single endpoint, what will be the result of this query?

{ user(id: "1") { name, posts { title } } }

GraphQL

query { user(id: "1") { name, posts { title } } }

A {"data": {"users": [{"name": "Alice"}]}}

B {"data": {"user": {"name": "Alice"}}}

C {"data": {"user": {"name": "Alice", "posts": [{"title": "Hello World"}, {"title": "GraphQL Rocks"}]}}}

D {"error": "Field 'posts' not found"}

💡 Hint

Look at the query requesting user name and posts titles.

The query asks for user with id 1, including their name and posts titles, so the response includes both.

📝 Syntax

advanced

Which GraphQL query syntax is correct for fetching nested data from a single endpoint?

Select the syntactically correct GraphQL query to fetch a user's name and their posts' titles.

A { user(id: "1") { name posts: { title } } }

B { user(id: "1") { name posts { title } } }

C { user(id: "1") { name; posts { title } } }

D { user(id: "1") { name, posts { title } } }

💡 Hint

Remember that GraphQL uses commas to separate fields, not semicolons or colons in this context.

Option D uses correct syntax with commas separating fields and proper nesting.

❓ optimization

advanced

How does single endpoint architecture optimize data fetching in GraphQL?

Which option best explains how single endpoint architecture helps optimize data fetching?

A It caches all data on the client side automatically.

B It allows clients to specify exactly which fields they want, reducing over-fetching and under-fetching.

C It forces the server to send all data for every query.

D It requires multiple endpoints to optimize different data types.

💡 Hint

Think about how clients control the data they receive in GraphQL.

Single endpoint lets clients request only needed fields, avoiding extra data transfer and improving efficiency.

🔧 Debug

expert

Why does this GraphQL query to a single endpoint fail with an error?

Given the query below, why does it produce an error?

{ user(id: 1) { name, posts { title } } }

Error: Argument "id" has invalid value 1.

GraphQL

query { user(id: 1) { name, posts { title } } }

A The id argument must be a string, so it should be "1" instead of 1.

B The user field does not accept any arguments.

C The posts field cannot be nested inside user.

D The query is missing a mutation keyword.

💡 Hint

Check the type of the id argument in the schema.

The id argument expects a string, so passing a number causes a type error.