Katkat

Company

Reddit interview questions

36 practice questions in the style of Reddit's interviews, covering Machine Learning, Behavioral & Leadership, Analytics & Experimentation, Software Engineering Fundamentals, ML System Design, System Design, Coding & Algorithms, Statistics & Math, Data Manipulation (SQL/Python).

Questions36

7 easy20 medium9 hard

Your progress0/36

Reddit interview questions by the numbers

Last updated

Katkat has 36 Reddit interview questions. The largest topics are Coding & Algorithms (22%), Behavioral & Leadership (19%) and ML System Design (17%). By difficulty: 19% easy, 56% medium and 25% hard. The most common round is Onsite (53%). Frequent concepts include A/B Testing, Causal Inference, Ranking and System Design.

Topics

Difficulty

  • Easy19% · 7
  • Medium56% · 20
  • Hard25% · 9

Interview rounds

  • Onsite53% · 19
  • Technical Screen47% · 17

Roles

  • Machine Learning Engineer39% · 14
  • Software Engineer33% · 12
  • Data Scientist25% · 9
  • Backend Engineer3% · 1

Frequent concepts

  • A/B Testing8% · 3
  • Causal Inference8% · 3
  • Ranking8% · 3
  • System Design8% · 3
  • Algorithms6% · 2
  • Arrays6% · 2

Most mentioned in interview experiences

  1. 1.Build and evaluate click prediction models1 report
  2. 2.Design a Comment-Likelihood Prediction System with a Focus on Feature and Model Serving1 report
  3. 3.Design Tennis Scoring with Pluggable Rules1 report
  4. 4.Exclude Cat- or Dog-Related Comments and All Their Replies by Reader Mode1 report
  5. 5.Explain and Reduce Position Bias in Ranking1 report
  6. 6.Explain How You Use AI in Engineering Work1 report
  7. 7.Find a Word Along One Fixed Direction in a Grid1 report

Counted from 4 candidate interview experiences on Katkat. How we collect and count

Showing 31–36 of 36 results

  • Merge Message Context WindowsMedium

    This problem tests your ability to merge overlapping intervals efficiently using sorting and greedy techniques, a foundational skill for data reconciliation tasks.

    RedditSoftware EngineerCoding & AlgorithmsOnsite
  • Model y from x and interpret distributionsMedium

    This question evaluates modeling judgment in machine learning, covering problem framing (regression versus classification), baseline model and metric selection, interpretation of feature or class distribution differences, and cold-start strategies for users, items, and regions.

    RedditMachine Learning EngineerMachine LearningOnsite
  • Moderator System with Ranking, Communities, and DemotionMedium

    Design and implement an in-memory moderator management system supporting community-specific hierarchies, seniority-based permissions, and rank mutations.

    RedditSoftware EngineerCoding & AlgorithmsTechnical Screen
  • Prioritize competing engineering requestsEasy

    This question evaluates a data scientist's prioritization, stakeholder management, trade-off communication, and leadership competencies when balancing competing analytics and experimentation requests.

    RedditData ScientistBehavioral & LeadershipOnsite
  • Query US-based users and most active forumsMedium

    This question evaluates SQL data manipulation skills, including time-based filtering, joins, aggregations, null-safe handling, ratio computation, distinct counts, and top-N ranking to determine user residency and forum activity.

    RedditData ScientistData Manipulation (SQL/Python)Technical Screen
  • Solve palindrome and list tasksHard

    This problem tests your ability to manipulate string prefixes to satisfy palindromic properties and your skill in performing in-place linked list reordering based on node index parity.

    RedditMachine Learning EngineerCoding & AlgorithmsOnsite

Reddit interview experiences

All 5 →
  • A Word-Search Rule Clarified Too LateReddit · Software Engineer · Technical Screen · Sep 2026
    Rejected

    The author reports an unsuccessful Reddit coding screen involving word search. After presenting the task, the interviewer remained quiet while the applicant worked. The author did not confirm the movement rules and implemented a more permissive search than the interviewer expected. A typo also consumed about ten minutes. Although the applicant’s own tests passed, the interviewer said near the end…

  • Onsite with a Cat/Dog Comment-Tree Filter and a Comment-Likelihood ML DesignReddit · Machine Learning Engineer · Onsite · Sep 2026

    Coding: seems like a new question? I had AI rewrite it: You are given a dictionary of Reddit comments. Each comment contains: id parent_comment body cat: whether the comment is about cats dog: whether the comment is about dogs Example input: Comments form a tree using parent_comment. There are two user modes: CAT_PERSON: does not want to see dog-related comments DOG_PERSON: does not want to see c…

  • General Pooling and a Ranking InterviewReddit · Machine Learning Engineer · Onsite · Aug 2026
    Rejected

    I applied to a particular team while sending out lots of applications online. The first phone screen was a question from the forum: analyze a spent-hours dataset and predict clicks. Since I had prepared it, the interview went quite smoothly. A week after the interview, I still hadn't heard anything, so I logged into the candidate portal. The position I had applied for was gone, and the interview…

  • Reddit Machine Learning Engineer interview experience: two DSA roundsReddit · Machine Learning Engineer · Technical Screen · Jul 2026

    The interview was straightforward: two data-structures-and-algorithms rounds along with machine-learning knowledge. The interviewers were kind and easygoing, and one of them in particular made the conversation feel comfortable. The format matched what I expected for the role. There were no strange surprises, just a clean sequence with a relaxed tone. I did not receive an offer, but the interview…

  • Load Balancer Deep-Dive and a One-Week OfferReddit · Backend Engineer · Technical Screen · May 2026
    Offer

    General coding 1: the Report Chain problem General coding 2: the Tennis Game problem — afterward the interviewer also chatted with me a bit about the strategy pattern Backend programming: the Load Balancer problem: It's split into four parts, and they give you a codebase. Part 1: The load balancer keeps getting error code 500. You need to find the cause — the cause is that the LB has the hostname…

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