Twitter / X

Twitter / X

Real-time social platform with petabyte-scale data and ML ranking systems.

4 Rounds ~14 Days Hard
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The Interview Loop

Recruiter Screen (30 min)

Standard fit check, behavioral questions, and resume overview.

Technical Loop (3-4 Rounds)

Deep dive into domain knowledge, coding, and system design.

Interview Question Bank

Backend Engineer • Behavioral • medium

Tell me about a time you had to ship a critical feature under an extremely tight deadline. What trade-offs did you make?

#Delivery #Prioritization #Trade-offs
Practice
Backend Engineer • Behavioral • medium

Tell me about a time you strongly disagreed with a technical direction proposed by leadership. How did you handle it?

#Conflict Resolution #Communication #Ownership
Practice
Backend Engineer • Behavioral • medium

Tell me about a time you caused a production outage. What was the root cause, and what did you learn?

#Accountability #Post-mortems #Learning
Practice
Backend Engineer • Behavioral • medium

Tell me about a time you had to dive into an undocumented, legacy codebase to fix a critical bug.

#Problem Solving #Adaptability #Debugging
Practice
Backend Engineer • Behavioral • medium

How do you prioritize technical debt versus shipping new features in a fast-paced environment?

#Prioritization #Technical Debt #Productivity
Practice
Backend Engineer • Coding • easy

Implement a function to parse a tweet string and extract all unique hashtags and user mentions, returning them in the order they appeared.

#String Manipulation #Regex #Hash Set
Practice
Backend Engineer • Coding • medium

Given a stream of tweets, write an algorithm to find the top K trending hashtags over the last 1 hour.

#Heap #Hash Map #Sliding Window
Practice
Backend Engineer • Coding • medium

Given a list of user connections (follower/following), write a function to find the shortest connection path between two users (Degrees of Separation).

#Graph #BFS #Bidirectional BFS
Practice
Backend Engineer • Coding • medium

Write a function to implement an LRU (Least Recently Used) Cache. This is often used for caching user profiles in memory.

#Linked List #Hash Map #Design
Practice
Backend Engineer • Coding • medium

Given an array of intervals representing active ad campaigns, merge all overlapping intervals to find the total continuous time ads are running.

#Array #Sorting #Intervals
Practice
Backend Engineer • Coding • hard

Write an algorithm to serialize and deserialize a tree of threaded replies (N-ary tree) to a string and back.

#Tree #DFS #Serialization
Practice
Backend Engineer • Coding • medium

Implement a Trie (Prefix Tree) to support autocomplete for user handles (@mentions).

#Trie #Design #String
Practice
Backend Engineer • Coding • medium

Given a list of tweets with timestamps, find the maximum number of tweets published within any 5-minute sliding window.

#Sliding Window #Two Pointers #Array
Practice
Backend Engineer • Coding • medium

Write a function to detect if there is a cycle in a retweet chain (represented as a directed graph).

#Graph #DFS #Cycle Detection
Practice
Backend Engineer • Coding • easy

Given two arrays representing the followers of User A and User B, write a function to return their mutual followers. Optimize for large arrays.

#Array #Hash Set #Two Pointers
Practice
Backend Engineer • Coding • hard

Implement a basic LFU (Least Frequently Used) Cache.

#Hash Map #Linked List #Design
Practice
Backend Engineer • Coding • easy

Given a string containing a tweet, check if it is a palindrome, ignoring spaces, punctuation, and casing.

#String #Two Pointers
Practice
Backend Engineer • System Design • hard

Design a distributed rate limiter for the X API to handle different tiers of users (Free, Basic, Pro) with varying limits.

#Distributed Systems #Rate Limiting #Redis
Practice
Backend Engineer • System Design • medium

Design the 'View Count' feature for tweets that was recently rolled out. How do you ensure high throughput and low latency without overwhelming the database?

#Caching #Event Sourcing #Data Aggregation
Practice
Backend Engineer • System Design • hard

Design the 'For You' timeline. How do you mix algorithmic recommendations with tweets from people the user follows?

#Recommendation Systems #Fan-out #Machine Learning Infrastructure
Practice
Backend Engineer • System Design • hard

Design the backend for Community Notes. How do you handle concurrent edits, version history, and fast retrieval?

#Concurrency Control #Database Design #Eventual Consistency
Practice
Backend Engineer • System Design • medium

Design Twitter's URL shortener (t.co). Focus on high availability and analytics tracking.

#Hashing #Database Sharding #Analytics
Practice
Backend Engineer • System Design • hard

Design a real-time spam/bot detection system that evaluates tweets as they are published.

#Stream Processing #Machine Learning #Rules Engine
Practice
Backend Engineer • System Design • hard

Design the Direct Message (DM) system. How do you handle real-time delivery, read receipts, and offline users?

#WebSockets #Pub/Sub #Database Design
Practice
Backend Engineer • System Design • hard

Design a notification system that sends push notifications to millions of users simultaneously when a major news event occurs.

#Push Notifications #Queueing #Scalability
Practice
Backend Engineer • System Design • medium

Design a system to securely store and serve media (images/videos) uploaded by users.

#Blob Storage #CDN #Media Processing
Practice
Backend Engineer • System Design • medium

Design a Distributed ID Generator (like Snowflake) to generate unique IDs for tweets at a massive scale.

#Distributed Systems #ID Generation #Concurrency
Practice
Backend Engineer • Technical • hard

How would you handle a 'Thundering Herd' problem when a celebrity with 100 million followers tweets, and millions of users try to reply or like it simultaneously?

#Concurrency #Caching #Load Balancing
Practice
Backend Engineer • Technical • medium

Explain how Kafka partitions work. If a consumer group is lagging behind the producer in a timeline ingestion topic, how do you troubleshoot and resolve it?

#Kafka #Message Queues #Troubleshooting
Practice
Backend Engineer • Technical • hard

You are tasked with migrating a legacy monolithic service to microservices to reduce compute costs. How do you approach this with zero downtime?

#Microservices #Migration #Strangler Fig Pattern
Practice
Backend Engineer • Technical • medium

How would you optimize a slow PostgreSQL query that is fetching a user's timeline and joining multiple tables (users, tweets, media)?

#SQL #Indexing #Query Optimization
Practice
Backend Engineer • Technical • medium

Discuss the trade-offs between using gRPC vs REST for internal microservice communication at X.

#Networking #gRPC #API Design
Practice
Backend Engineer • Technical • hard

How do you handle eventual consistency in a distributed database? Give an example of where strict consistency is required vs where eventual consistency is acceptable at X.

#CAP Theorem #Consistency Models #Databases
Practice
Backend Engineer • Technical • hard

Explain how garbage collection works in the JVM. How would you tune it for a high-throughput backend service?

#JVM #Garbage Collection #Performance Tuning
Practice
Backend Engineer • Technical • medium

You notice a sudden spike in 503 Service Unavailable errors on the Timeline service. Walk me through your troubleshooting steps.

#Incident Response #Monitoring #Debugging
Practice

Difficulty Radar

Based on recent AI-sourced data.

Meet Your Interviewers

The "Standard" Interviewer

Senior Engineer

Focuses on core competencies, system constraints, and clear communication.

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Unwritten Rules

Think Out Loud

Always explain your thought process before writing code or drawing architecture.

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