Reddit Data Scientist Interview Questions

1.Tell me about a time you shipped an imperfect data solution because waiting for the perfect approach would have delayed an important business decision. What trade-offs did you make?

2.Tell me about a time you had to quickly scale up data collection or analysis capabilities to support a sudden increase in traffic or user activity. What was your response time and approach?

3.Tell me about a time you had to optimize a model or data pipeline to handle significantly more data or users than it was originally designed for. What was your approach and what challenges did you face?

4.Describe a project where you used data to advocate for a feature or approach that would better serve underrepresented users or use cases, even if it wasn't the obvious business priority.

5.Describe a time when you had to design or modify a data product where the impact on different user communities was a key consideration. How did you balance competing needs?

6.Walk me through a time when you had to build safeguards into a model or data system to prevent misuse or adversarial behavior. What specific threats were you concerned about?

7.You're tasked with building a content quality classifier that can help moderators identify low-effort posts. How would you approach this problem while ensuring the model doesn't unfairly penalize certain types of content or communities?

8.You notice that our search results are performing well for popular queries but poorly for long-tail searches that are specific to niche communities. How would you investigate and improve this?

9.Our recommendation system serves billions of posts to users daily, but we notice certain communities consistently get less exposure despite quality content. How would you investigate this bias and design a solution to improve discovery equity across communities?

10.Walk me through how you'd design an experimentation framework to test changes to Reddit's ranking algorithm, considering that different communities have vastly different engagement patterns and user behaviors.

11.You need to build a real-time anomaly detection system for detecting brigading and coordinated inauthentic behavior across Reddit's communities. What approach would you take and what data would you need?

12.Reddit's advertising system needs to balance revenue optimization with user experience and community standards. How would you design a machine learning approach to determine which ads to show without disrupting authentic community conversations?

13.Build a system to measure and improve content discovery for Reddit's smaller communities that often get overshadowed by larger subreddits in recommendations and search results.

14.Reddit needs to build a system that can automatically classify and route user reports about harmful content to the appropriate human reviewers. How would you design this to handle millions of reports daily while ensuring consistent review quality?

15.Reddit's mobile apps need to surface personalized content recommendations even when users are offline. Design a system that can pre-compute and cache relevant posts for millions of users across thousands of communities.

16.Design a data system that can track content moderation actions across Reddit's millions of communities to identify patterns of inconsistent enforcement and help moderators maintain fair standards.

17.Design a data pipeline that can process user voting patterns across all of Reddit's communities to detect potential vote manipulation in real-time. How would you handle the scale of billions of votes per day while maintaining low latency for enforcement actions?

18.Design a real-time analytics system for Reddit's advertising platform that can provide campaign performance insights to advertisers while protecting user privacy and community data.

19.Tell me about a time you had to convince engineers or product managers to adopt a data-driven approach when they preferred to rely on intuition or existing processes.

20.Tell me about a time you had to coordinate multiple data science projects or initiatives across different teams when you didn't have formal authority over the other contributors.

21.Describe a situation where you had to lead a project with unclear requirements where different teams had competing priorities. How did you navigate to a solution?

22.Tell me about a time you identified a potential negative impact your work could have on specific communities or user groups and how you addressed it.

23.Walk me through a time when you had to make a judgment call about data quality or methodology when there wasn't a clear right answer and you couldn't wait for more information.

24.Describe a time when you had to influence senior leadership or executives to change course on a data or analytics initiative. What was your approach?

25.Reddit's daily active users dropped 3% yesterday with no new deployments or incidents. Walk me through how you'd investigate this, starting with your first steps.

26.Estimate how many unique users visit Reddit's front page versus specific subreddit pages in a typical day. Walk me through your reasoning.

27.Reddit wants to expand into a new international market. What metrics would you track in the first 6 months to determine if the expansion is successful?

28.Our data shows that 15% of new Reddit accounts are abandoned within 24 hours. Design an analysis to understand why and identify the highest-impact interventions.

29.Reddit's advertising revenue per user varies dramatically between different communities. Design a framework to fairly allocate ad inventory while maintaining community authenticity and user experience.

30.Design a data system to measure the health of Reddit's moderator ecosystem across all communities, considering that moderation styles and needs vary dramatically between different types of subreddits.