Design a GraphQL API for a social feed
PremiumAPI designMedium
- GraphQL
- DataLoader batching
- Query complexity limits
Quick answer
This API design interview question asks you to design a GraphQL API for a social feed. Aim for a design that exposes a clear, consistent and safe interface, then explain the resources, requests, responses and error handling. Interviewers want to see how you name resources, version the interface and handle failure cases.
The problem
Design a GraphQL API for a social feed like Instagram's: one schema that replaces twelve REST endpoints so mobile and web fetch posts, authors, counts and comments in one round trip. The hard parts are avoiding N+1 lookups and stopping any query from overloading the backend.
The feed shows posts from followed users, each with author, media, like and comment counts, whether the viewer liked it, and the first two comments. Users can like, comment, follow and post. Design the GraphQL schema and the rules around it.
What must a GraphQL API for a social feed do?
- Feed query: Fetch a page of posts with author, media, counts, viewer state and the first N comments in one request.
- Mutations: createPost, likePost, unlikePost, addComment, follow, unfollow, each returning the updated object.
How well must it do it?
- No N+1: Fetching 20 posts with authors must not make 20 author lookups.
- Cost control: No query may cause more than a bounded amount of backend work, regardless of nesting.
What scale should you design for?
Use these numbers in your estimates.
The scale numbers unlock with this questionUnlock
Key concepts
- GraphQL
- DataLoader batching
- Query complexity limits
- Persisted queries
- Relay connections
- Schema evolution
How you’ll practise
- Use cases
- Resources
- Endpoints
- Errors, auth and limits
- Versioning
- Wrap-up
Lala, personalized to you, gives a hint when you ask and reviews your design when you are ready.
What do interviewers look for?
In any API design round.
- Starts from the clients and the use cases
- Names resources and operations consistently
- Defines request and response shapes and status codes
- Covers authentication, rate limits and idempotency
- Plans pagination, filtering and versioning
- Explains how clients learn about and recover from errors
Questions people ask about this interview question
- Which design type is this question?
- It is an API design question. You design a GraphQL API for a social feed and explain your choices the way you would in an interview.
- Is this question asked at entry level?
- It is marked Medium. Entry-level engineers can practise it, but it expects you to reason about requirements and trade-offs, not only list components.
- What should I cover first?
- Start with the clients, the main use cases and the resources they need. Agree on scope with the interviewer before you design anything.
- Can I practise it for free?
- It is a premium question. Sign up and unlock it once for 10 credits; it then stays unlocked. When you finish, Lala, your personalized AI mentor, can review your design for 30 credits.
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Updated · Written by the SevyDevy team