Reddit is a globally recognized content community platform known for its powerful back-end architecture and large-scale data processing capabilities. Its technical team advocates simplicity, engineering thinking and system stability. Many students may feel that Reddit is not a typical big factory, but in fact, its technical challenges and interview difficulty does not lose FAANG! This post will share some Reddit high-frequency interview questions, as well as some students widely recommended preparation strategies (Reddit interview tips), to help you get through!
Reddit interview process: It’s no longer just a matter of answering questions
Unlike Google or Meta, Reddit interviewers are very averse to "questioning people." They value more whether you can write Production-Ready (production-grade) code.
1. OA (Online Assessment) & Phone Screen
- Platform: Typically CoderPad or Karat is used.
- Features: The difficulty level of the questions is Medium, but the coding style is required to be perfect.Must be able to pass all Test Cases,Reddit-interview-tips-reddit-Interview experience sharing | Frequent questions-Full analysis of preparation suggestions
- Avoid pitfalls: Don’t just pursue the best solution and write code that’s hard to read. Reddit engineers take readability very seriously.
2. Virtual Onsite (VO)
Typically consists of 4-5 rounds of 45-60 minutes each:
Culture / Behavioral (1 round): Check whether you are consistent with the value of “Remember the Human”.
Practical Coding (2 rounds): Often based on real business scenarios (such as feed stream processing, text parsing).
System Design (1-2 rounds): Focus on examining data consistency and caching strategies under high concurrency.
Sharing of interview questions
When we coached students, we found that the following two types of questions appeared very frequently in recent Reddit Data Engineer and SWE interviews.
Sub-section post heat calculation
Background Description:
Every subreddit on Reddit sorts posts based on their hotness. Now you are asked to implement a simplified version of the heat model that, given the upvotes, downvotes, and posting time of each post, calculates its heat score and returns the top K posts.
Require:
Use the following heat function (a simplified version of Hacker News):
hot_score = (upvotes - downvotes) / (hours_since_posted + 2)^1.5
Returns the top K post IDs in descending order of hot_score.
Analog user reporting system
Background Description:
Reddit allows users to report posts that violate the rules. You need to implement a module that counts how many unique users have reported a post in a 24 hour period and can always check if the current number of reports exceeds a threshold.
Enter the operation:
report(user_id, post_id, timestamp): Record reporting
is_flagged(post_id, current_time): Determine if a post exceeds the reporting threshold (e.g. 10 reports)
Subreddit Classified Recommender System
Background Description:
Reddit wants to suggest similar communities based on the subreddits where users are active. Please design a simple data model & algorithm to implement "subreddits you might be interested in".
Reference design elements:
Each subreddit can be represented by keywords
Historical user access behavior as input
Returns a list of subreddits with a high degree of overlap with their interests
Why can't I pass the Reddit interview by just "gripping questions"?
Reddit's engineering culture is quite unique. We once met a Data Analyst trainee with 3 years of experience. His technical foundation was acceptable, but he was very anxious when facing this kind of "non-standard" interview and worried that he would not be able to respond on the spot.
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