ZorixOS
5+ Reddit questions

Reddit interview questions and how to prepare

The questions candidates report from Reddit interviews, sorted by how often they come up, with difficulty and topics, plus original practice written in Reddit's interview style.

Practice Reddit questions free All companies

ZorixOS tracks 5 community-reported Reddit interview questions, drawn from an open-source dataset of real interview reports and sorted by how frequently each one comes up. Every question links to its source. Alongside them are 98 original ZorixOS practice questions written in Reddit's known interview style (not claimed as asked at Reddit), so you can rehearse the real format. Practice any of them out loud in a free AI mock interview tuned to Reddit.

Updated July 2026

Reddit interview questions candidates report

Community-reported from real Reddit interviews (open-source dataset), most-asked first. Showing 5. Each links to its source.

  1. Word Ladder
    Hash TableStringBreadth-First Search
    Hard100% asked
  2. Number of Ways to Buy Pens and Pencils
    MathEnumeration
    Medium96% asked
  3. LRU Cache
    Hash TableLinked ListDesignDoubly-Linked List
    Medium81% asked
  4. Design Hit Counter
    ArrayBinary SearchDesignQueue
    Medium75% asked
  5. Logger Rate Limiter
    Hash TableDesignData Stream
    Easy75% asked

Practice questions in Reddit's style

Original ZorixOS questions written the way Reddit interviews, so you rehearse the real format. Not claimed as asked at Reddit.

  1. Imagine a Reddit user reports that their upvote count on a popular post is suddenly fluctuating wildly, sometimes going up, sometimes down by thousands within minutes, even though new comments and upvotes are still coming in steadily. How would you debug this issue, assuming it's not a simple display bug?

    Software EngineerDebuggingTests: Evaluates systematic debugging approach under pressure and understanding of distributed systems.

  2. Reddit's feed ranking algorithm needs to balance showing new, engaging content with surfacing evergreen or highly-rated older content. Design a system for ranking posts within a subreddit that accounts for both recency and overall 'hotness' (combining upvotes and time). Consider potential challenges like vote manipulation.

    Software EngineerSystem DesignTests: Evaluates ability to design scalable systems and reason about algorithmic trade-offs.

  3. You've noticed that certain subreddits, especially those with a lot of user generated media like images or videos, are experiencing very high latency when loading posts with many media attachments. What are the potential causes, and how would you design a solution to improve load times for these posts at Reddit's scale?

    Software EngineerSystem DesignTests: Evaluates understanding of performance bottlenecks and scalable solutions for rich content delivery.

  4. Reddit uses a distributed system for storing and serving comments. If a user reports that a specific comment thread seems to be missing some replies that they know exist, how would you approach diagnosing the root cause, considering potential issues like eventual consistency, replication lag, or data corruption?

    Software EngineerDebuggingTests: Evaluates debugging skills in a distributed, eventually consistent environment.

  5. Consider Reddit's 'Trending' sidebar. How would you design the system that determines which subreddits and posts appear there? What data would you use, and what are the potential challenges in ensuring it's relevant, timely, and not easily gamed?

    Software EngineerSystem DesignTests: Evaluates system design thinking, especially for real-time, personalized features.

  6. Reddit wants to implement a feature to automatically detect and flag potentially harmful content (e.g., hate speech, misinformation) before it gets reported. Outline a high-level system design for this, considering the trade-offs between false positives and false negatives, and how to integrate human moderation.

    Software EngineerSystem DesignTests: Evaluates system design for content moderation, considering ML integration and ethical implications.

92+ more Reddit-style questions are in the free library, each practiceable live with adaptive follow-ups and an honest scorecard. Start free.

Keep exploring

Can you answer these out loud, under Reddit-style follow-ups?

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Reddit Interview Questions (2026) | ZorixOS