Meta Interview Questions 2026

Design Facebook's News Feed ranking system. How do you score posts from thousands of friends and pages? Cover: candidate generation, feature extraction, ML ranking model, how you handle near-real-time freshness, and edge vs server-side ranking for mobile clients.

Design Facebook Live - a system to stream live video from one user to potentially millions of concurrent viewers with low latency. Cover: ingest pipeline, transcoding, CDN edge caching, adaptive bitrate, and how you handle a celebrity going live.

Design WhatsApp's end-to-end encrypted messaging system. How do you exchange keys, store messages server-side without reading them, and handle multi-device sync? Cover the Signal Protocol basics.

Design Instagram Stories. A story disappears after 24 hours and is shown in a ring around profile pictures. Cover: upload pipeline, storage with TTL, efficient delivery to followers, and view count tracking at scale.

Design Instagram feed — a user follows 500 people, each posts 2-3 times daily. How do you generate and serve a personalized, ranked feed at scale?

Given Meta's social graph, find all friend-of-friend recommendations for a user that are not already friends. Discuss BFS at scale, how to prune the search space, and how to rank recommendations by mutual friend count efficiently.

Given a social graph, find all users within K hops of a given user. Implement BFS with a visited set. Then discuss how you would scale this to Meta's 3 billion user graph using partitioning.

Given a social graph, find the shortest chain of mutual connections between two users (like LinkedIn's "degrees of connection"), and explain how bidirectional BFS improves performance over a single-direction BFS at this scale.

Tell me about a time you had to make a decision with incomplete data. Meta values moving fast — how did you balance the need for speed against the risk of being wrong? What would you do differently today?

Meta values moving fast. Describe a time you shipped something that later needed to be rolled back or significantly reworked. What was the cost and what did you learn about the balance between speed and reliability?

Describe a situation where you had to ship a feature you personally disagreed with. How did you handle it, and would you make the same call again?

Explain how React's virtual DOM diffing algorithm (reconciliation) works. Why is it O(n) instead of O(n3)? What are the assumptions it makes and when do those break down (causing performance issues)?

Given an array of N integers, find the maximum product subarray. Explain why you need to track both the maximum and minimum product ending at each position, and handle zeros and negative numbers.

Your fine-tuned LLM performs well on your eval set but users report degraded responses 2 weeks after deployment. What is happening and what do you do?

What is the difference between RANK(), DENSE_RANK(), and ROW_NUMBER()? Give a real use case for each.

What is the difference between useMemo and useCallback? Give concrete examples of when each actually helps vs. when it hurts.

A news feed component re-fetches and re-renders every item whenever a single like count changes. Walk through how you would restructure state so only the affected item re-renders, without introducing a global state library.

Design the "who viewed your profile" feature for a professional network with 500M users. Discuss write amplification, retention policy, and privacy controls for who can see the data.

Explain the output order of this code and why: console.log(1); setTimeout(()=>console.log(2),0); Promise.resolve().then(()=>console.log(3)); console.log(4);

You have a Kafka topic with 6 partitions and a consumer group with 10 consumer instances. What happens to the 4 extra consumers, and why is over-provisioning consumers like this a mistake?

What is a memory leak in Java despite having a garbage collector? Give a concrete example involving a static collection.