#### 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]** [View Details](/content/community/questions/online-chess-platform/cm4szywgj003ivszmblm3pmoa/index.html) --- ### 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]** [View Details](/content/community/questions/job-scheduler-cron-history/cm7w828yv00sejmejlmofwtvp/index.html) --- ### 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]** [View Details](/content/community/questions/messenger-chat-system/cm4szunov00303g2e2gomqo2j/index.html) --- ### 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]** [View Details](/content/community/questions/news-aggregator-feed/cm96lh25n0039ad08067audlg/index.html) --- ### 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]** [View Details](/content/community/questions/notification-system-scale/cm758vf17024kalw2qn7e57xs/index.html) --- ### 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]** [View Details](/content/community/questions/payment-batch-processing/cmavpegdk0067ad08ujhdbrjk/index.html) --- ### 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]** [View Details](/content/community/questions/donations-website-charities/cmbdisew101kuad08fuuiky5v/index.html) --- ### 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]** [View Details](/content/community/questions/book-seller-platform/cm8j5hkhi009ouxg8w34ni7nd/index.html) --- ### 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]** [View Details](/content/community/questions/drone-delivery-time/cmo91yfsk00kc08adrbzu0xmq/index.html) --- ### 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]** [View Details](/content/community/questions/distributed-rate-limiter/cm6i9mhd800nz41cd0xx20r8p/index.html) --- ### 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]** [View Details](/content/community/questions/follow-graph-recommendations/cmobtcld30s420fadjyp8zgv3/index.html) --- ### 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]** [View Details](/content/community/questions/http-route-matching/cmou3jp0m13rl0cadz84s19xd/index.html) --- ### 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]** [View Details](/content/community/questions/top-k-counts/cm4t0twp0004pvszmvb2qeg0u/index.html) --- ### 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]** [View Details](/content/community/questions/dasher-payout-classes/cmdckvv0i008qad08os5l6gv2/index.html) --- ### 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]** [View Details](/content/community/questions/lru-cache/cm5eh7nrh04r2838os7lk8nwf/index.html) --- ### 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]** [View Details](/content/community/questions/sliding-window-rate-limiter/cmni1bvsy02uw0dadl09u4g1r/index.html) --- ### 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]** [View Details](/content/community/questions/merge-intervals/cm5eh7nrh04ok838oa0xi845w/index.html) --- ### 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]** [View Details](/content/community/questions/ticket-booking-system/cm4szwvht003pnqlrkhad2xjd/index.html) --- ### 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]** [View Details](/content/community/questions/chatbot-design/cmg6up3jj030x08adrb73umuk/index.html) --- ### 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]** [View Details](/content/community/questions/feature-flag-service/cmb8nw8vo00ybad08tftfys92/index.html) --- ### 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]** [View Details](/content/community/questions/most-called-function/cmkoudbop0kuj08adzolpty17/index.html) --- ### 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]** [View Details](/content/community/questions/number-islands/cm5eh7nrh04sk838olttm8wc3/index.html) --- ### 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]** [View Details](/content/community/questions/ad-click-aggregator/cm4t0kxb6004488il22wqa2nn/index.html) --- ### 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]** [View Details](/content/community/questions/flower-disease-spread/cmhykoavb02w108adtuubkyzp/index.html) --- ### 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]** [View Details](/content/community/questions/rain-water-puzzle/cm5eh7nrh04o6838odkoa0acw/index.html) --- **Real Interview Questions Database | Hello Interview**