LinkedIn Interview Questions 2026

Design LinkedIn's "People You May Know" feature. How do you compute second and third-degree connections for 900 million users efficiently? Discuss graph storage (adjacency list vs matrix), batch vs real-time computation, and how to refresh recommendations when someone adds a new connection.

Design LinkedIn's job recommendation engine. Given a user's profile, skills, and activity, rank the most relevant open positions. Cover candidate retrieval, feature engineering (skills overlap, company affinity, recency), and how you A/B test ranking changes at scale.

Design LinkedIn's feed. Each user sees posts from their connections, pages they follow, and sponsored content. Posts must be ranked by relevance. Cover: fan-out-on-write vs fan-out-on-read, feed generation for users with 30k connections, and freshness.

Design LinkedIn's InMail spam filtering system. Premium users can message strangers. How do you detect and block spam campaigns while allowing legitimate cold outreach? Cover: sender reputation, content analysis, and feedback loops.

LinkedIn is a professional network. Describe a project where you had to balance user privacy with platform analytics needs. What principles guided your decisions?

Tell me about a project where the requirements changed significantly midway through. How did you adapt your existing implementation?

How does LinkedIn's "Who viewed your profile" feature work? What data is stored, how long is it retained, and how do you provide the feature to free users (last 5 viewers) vs Premium (full list) without exposing premium-only data?

LinkedIn uses Kafka extensively. Explain how you would design the Kafka topic structure for LinkedIn's activity events (profile view, connection request, message sent). Cover: topic naming, partitioning strategy, consumer group design, and exactly-once semantics.

How does Airflow handle backfilling? Design a DAG that safely backfills 90 days of missing data without overloading the database.

Design the news feed ranking pipeline for a professional network. How do you balance freshness, relevance, and diversity of content sources without the feed feeling stale or repetitive?

Explain the difference between synchronized, ReentrantLock, and ConcurrentHashMap for protecting shared state in Java. When would you choose each?

Write a query to find the top 3 skills most commonly shared between pairs of connected users, given a UserSkills table and a Connections table.