Real Interview Questions Database
Real Interview Questions
13,098 total reports
Actual questions from recent interviews, shared by other Hello Interview users.
Design Online Chess
Type: System Design
Level: Junior-Senior Manager
Design a real-time chess platform similar to Chess.com that supports gameplay across multiple devices, move validation, matchmaking, leaderboards, and key features like move undo functionality.
[Reported by 148 users • Last Asked Late August, 2026]
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Design a Job Scheduler
Type: System Design
Level: Junior-Senior Manager
Design a distributed job scheduler that can handle high-throughput job processing (10,000+ jobs per second), support both scheduled (cron-based) and ad-hoc job execution, include retry mechanisms for failed jobs, and maintain execution history for up to one year.
[Reported by 153 users • Last Asked Mid August, 2026]
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Design a Chat/Messaging System
Type: System Design
Level: Mid-level-Senior Manager
Design a real-time messaging system like WhatsApp or Facebook Messenger that supports 1:1 and group conversations, message delivery status tracking, user presence features, conversation history, and can scale to handle millions of users.
[Reported by 177 users • Last Asked Late August, 2026]
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Design a News Aggregator System
Type: System Design
Level: Junior-Senior Manager
Design a news aggregation system like Google News that allows users to subscribe to different news sources, categories, and topics, then view a personalized real-time news feed based on their interests.
[Reported by 82 users • Last Asked Late August, 2026]
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Design a Notification System
Type: System Design
Level: Mid-level-Senior Manager
Design a scalable notification system that supports both individual and bulk notifications to multiple users. The system should handle different types of notifications including critical time-sensitive messages (like 1:1 chat) and promotional content (like system-generated recommendations) with appropriate delivery mechanisms. Consider scalability requirements (up to 1M notifications/second).
[Reported by 65 users • Last Asked Late August, 2026]
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Design a Payment System
Type: System Design
Level: Junior-Senior Manager
Design a payment system that processes transactions through an external payment service for approval/denial, holds approved amounts, and batches all transactions daily for final processing while handling 10,000 transactions per second.
[Reported by 87 users • Last Asked Late August, 2026]
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Design a Donations Website
Type: System Design
Level: Mid-level-Staff, Manager-Senior Manager
Design a short-term (24-48 hour) donations website where users can contribute to pre-selected charities, focusing on payment processing, failure handling, and backup payment methods.
[Reported by 61 users • Last Asked Late August, 2026]
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Design a Book Seller Platform
Type: System Design
Level: Mid-level-Senior Manager
Design a book marketplace platform that connects customers with multiple book sellers, allowing customers to submit purchase requests with their maximum price and automatically find the best deal from registered sellers.
[Reported by 91 users • Last Asked Late July, 2026]
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Minimum Delivery Time on Circular Ring
Type: Coding
Level: Junior-Senior
Given m nodes arranged in a circular ring where a drone can move to adjacent nodes with given transition times, calculate the minimum total travel time for the drone to fulfill all delivery requests starting from node 1.
[Reported by 19 users • Last Asked Mid August, 2026]
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Design a Rate Limiter
Type: System Design
Level: Mid-level-Senior Manager
Design a rate limiting system that can control and throttle API requests to prevent system overload and ensure fair resource allocation.
[Reported by 54 users • Last Asked Late August, 2026]
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Implement Follow Graph with Snapshots and Recommendations
Type: Coding
Level: Senior-Principal
Design and implement a social follow graph that supports snapshotting the state of relationships at a given point in time and generating friend/follow recommendations based on graph traversal.
[Reported by 21 users • Last Asked Late August, 2026]
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Implement HTTP Route Matching for a Web Framework
Type: Coding
Level: Junior-Staff
Implement two functions, registerHandler(pattern) and getHandler(path), that form the core routing logic of a web framework.
[Reported by 9 users • Last Asked Late August, 2026]
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Design a Top-K System
Type: System Design
Level: Intern-Senior Manager
Design a system that efficiently retrieves top-k items based on user activity or engagement metrics within specified time windows.
[Reported by 99 users • Last Asked Mid August, 2026]
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Design Dasher Payout Calculation System Based on Delivery Events
Type: Coding
Level: Mid-level-Staff
Design an API/class that calculates payout for a delivery driver based on delivery events from an external service.
[Reported by 52 users • Last Asked Late August, 2026]
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Leetcode 146. LRU Cache
Type: Coding
Level: Junior-Senior Manager
Implement an LRUCache that supports O(1) average-time get(key) returning the value or -1 and put(key, value).
[Reported by 107 users • Last Asked Late July, 2026]
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Sliding Window Rate Limiter
Type: Coding
Level: Mid-level-Senior
Implement a rate limiter using a sliding window algorithm that tracks and limits the number of requests allowed within a given time window.
[Reported by 10 users • Last Asked Late August, 2026]
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Leetcode 56. Merge Intervals
Type: Coding
Level: Junior-Manager
Given a list of intervals, merge all overlapping intervals and return the minimal set of non-overlapping intervals that cover them.
[Reported by 72 users • Last Asked Late August, 2026]
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Design a Ticket Booking System
Type: System Design
Level: Junior-Staff, Manager-Senior Manager, Senior Director
Design a ticket booking system like Ticketmaster that handles high-traffic events, supports both seated and general admission tickets, and manages scenarios like flash sales with limited inventory and concurrent users.
[Reported by 148 users • Last Asked Mid August, 2026]
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Design ChatGPT
Type: System Design
Level: Junior-Staff, Manager-Senior Manager
Design a conversational AI system similar to ChatGPT that allows users to have natural language conversations.
[Reported by 41 users • Last Asked Late August, 2026]
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Design a Feature Flag Service
Type: System Design
Level: Mid-level-Manager
Design a feature flag service that allows software teams to enable/disable features dynamically without code deployment.
[Reported by 44 users • Last Asked Late August, 2026]
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Find Most Called Function in Stack Trace
Type: Coding
Level: Mid-level-Staff
Given a list representing a stack trace, determine which function is called the most frequently.
[Reported by 9 users • Last Asked Late August, 2026]
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Leetcode 200. Number of Islands
Type: Coding
Level: Intern, Mid-level-Staff
Count the number of islands in an m×n binary grid.
[Reported by 27 users • Last Asked Late August, 2026]
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Design an Ad Click Aggregator
Type: System Design
Level: Mid-level-Senior Manager
Design a real-time ad click aggregator that processes billions of ad events daily, aggregates them with maximum 30-second latency, and supports both real-time dashboard queries and historical analytics for up to 2 years.
[Reported by 144 users • Last Asked Early August, 2026]
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Disease Spread in Flower Grid
Type: Coding
Level: Junior-Staff
Implement algorithms to simulate and analyze the spread of disease through flowers arranged in a grid structure.
[Reported by 33 users • Last Asked Early August, 2026]
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Leetcode 42. Trapping Rain Water
Type: Coding
Level: Junior-Senior
Given an array of non-negative heights representing elevation bars, compute the total units of water that can be trapped between them after raining.
[Reported by 17 users • Last Asked Late August, 2026]
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