Reddit Software Engineer Interview Questions
31+ questions from real Reddit Software Engineer interviews, reported by candidates.
Round Types
Top Topics
Questions
I’m looking to understand this from the point of view of experienced devs who have worked initially at non-recognizable firms and then made the switch to recognizable tech or non-tech companies. **Has
Word Search II
Word Search II Given a 2-D grid of characters `board` and a list of strings `words`, return all words that are present in the grid. For a word to be present it must be possible to form the word with
Dictionary Word Transformation Path ## Problem Overview You are given: * a `start` word * a `target` word * a dictionary of allowed words Determine whether the words can be connected by a valid tran
Report Chain
Report Chain ## Problem Overview You are given an org chart as a `list[list[str]]`. Each inner list has the form: ```python [manager, report_1, report_2, ...] ``` For example: ```python [["A", "B",
Tennis Score Game
Tennis Score Game ## Problem Overview Design a two-player game with three core methods: * `add_score(player)` * `get_score()` * `get_result()` The interview then adds a follow-up: convert the score
Design a Gaming Leaderboard Service Imagine you are building a backend service for game studios. Games run on players' computers, and after a game session ends the client wants to show two things ri
Design Reddit Live Chat Design Reddit Live Chat for large live events such as the Super Bowl. Users join a live discussion tied to a post or event, receive messages in real time, send messages if al
Moderator List Hierarchy ## Problem Overview Implement a Reddit-style moderator list from a newline-delimited log string. The interview usually comes in three parts: 1. A single mod list 2. Multiple
Merge Chat Message Windows ## Problem Overview You are given an existing API: ```python def get_chat_messages(message_id: int) -> list[Message]: ... ``` For a given `message_id`, it returns the surr
Logger Rate Limiter
Logger Rate Limiter Design a logger system that receives a stream of timestamped messages. A message may be printed only if the same message has not been printed in the last `10` seconds. Implement
Billing Status Replay (OOD)
Billing Status Replay (OOD) ## Problem Overview We accidentally dropped the database that stored the current billing state for advertisers. The old transaction logs still exist, so the task is to re
Multi part question from reddit tech screen. The problem should be code complete and should successfully execute the given test cases. Verdict: Reject interview time : 60 min Feedback:- Question has a lot...
I'll preface this by saying I feel incredibly fortunate to be in this position, but I have a final round interview in person for Jane Street next week and am pretty terrified. I'm first gen/low income
Datadog | onsite | design reddit r/places
I have a datadog on site coming up soon and I\'ve seen a few people posted this as their system design question on glassdoor Description: Design an app in the style...
When is RDS really the better choice over something NoSQL like DynamoDb?
**TL;DR:** Have I been indoctrinated into believing that NoSQL solutions like DDB (DynamoDB) are always the better architectural pattern, or are there valid scenarios to build a service on top of SQL.
**Intro** I'm about to start a project and I'd appreciate some input from the good people of Reddit. I'm not doing this by myself but I'm the most experience developer on the team which is why I'm req
I'm a senior engineer with 8 years of experience facing a career roadblock. My current work lacks in speed, thoroughness, and effective refactoring. Upon self-reflection and feedback from managers, I'
About a month ago I posted about [my project](https://puter.com/app/editor?c=1) on /r/programming ([the post](https://www.reddit.com/r/programming/comments/v45rb6/i_spent_a_year_building_a_desktop_env
Reddit - phone screen - front end - reject
The phone screen was over google hangouts plus a code sharing site. The first part of the interview was general knowledge. Again, this is front end. What is cross site...
My Reddit account cost me my next SDE job(95% sure)
So, this happened, I got rejected for- having a reddit account and being unbelievably stupid. I am Senior software engineer and was interviewing for a startup which just got huge funding. I got throug
What Reddit Looks for in Software Engineer Interviews
Reddit Software Engineer interviews are calibrated against the level and scope expected of the role. Across 31+ verified candidate reports on LeakCode, the consistent signals interviewers look for: clear problem decomposition before coding, explicit complexity reasoning, structured handling of edge cases, and the ability to articulate trade-offs between two reasonable approaches.
The discriminator between candidates who advance and candidates who do not is rarely the final correctness of the solution. It is the path to the solution: did you ask clarifying questions, did you state your approach before coding, did you handle edge cases without prompting, and did you communicate your reasoning throughout. Reports tagged "no hire" frequently cite a working solution with poor communication; reports tagged "strong hire" cite clear thinking even when the final solution was incomplete.
How To Use This Question Set
Real interview reports are a calibration tool, not a memorization target. Companies update their question pools every 2-4 months; memorizing exact problems risks misleading you when the interviewer uses a variant. The high-leverage use: identify the patterns that appear repeatedly in Reddit Software Engineer reports, practice those patterns on similar (not identical) problems, and use the reports to understand the interviewer's typical follow-up depth.
Filter the questions below by round type, difficulty, and recency. Focus first on reports from the past 6-12 months; older reports may reference questions that have since rotated out of Reddit's pool. Reports tagged with quantified difficulty (e.g., "medium-hard") are higher-signal than reports without difficulty tags.
Round-by-Round Expectations
Reddit Software Engineer loops typically span 4-6 rounds across phone screens and on-site or virtual on-site interviews. The structure varies by company: some run 1 recruiter screen + 1 technical phone + 3-4 on-site rounds; others run 1 recruiter screen + 1 OA + 4-5 on-site rounds. The recruiter screen is logistics and culture-light; the technical phone screen is medium-difficulty coding; the on-site loop covers coding, system design (at L4+ levels), and behavioral rounds.
Each round is designed to surface a specific signal. Coding rounds: correctness, code quality, complexity reasoning, communication. System design rounds: requirements clarification, design judgment, operational thinking. Behavioral rounds: ownership scope, leadership, ambiguity tolerance, conflict navigation. Strong candidates explicitly hit each signal dimension out loud during the round; weak candidates focus only on solving the prompt.
Common Interview Mistakes At This Combination
Reports tagged "no hire" at Reddit Software Engineer commonly cite: jumping into code without clarifying requirements, coding silently for 10+ minutes without verbalizing approach, missing edge cases (empty input, single element, very large input, overflow), and producing a working solution that the candidate cannot explain or refactor when probed. Strong candidates avoid these patterns by following a consistent template: clarify, verbalize approach, code with narration, test with examples.
Behavioral and design rounds have their own failure modes. Behavioral: stories that use "we" instead of "I" diluting individual signal, stories with no quantified outcome, defensiveness when probed about failure. Design: not asking clarifying questions, not stating requirements out loud, designing for a single server when the prompt clearly implies scale, ignoring operational concerns (deployment, monitoring, rollback). These show up in roughly half of Reddit Software Engineer interview retrospectives on LeakCode.
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