Reddit Interview Questions
Practice the exact questions companies are asking right now.
Build and evaluate click prediction models
Click-Through Rate (CTR) Prediction: Build, Compare, and Justify Models Context You are given a tabular dataset for binary click prediction (click = 1...
Measure impact of ads-manager automation feature
Context An Ads Manager product has new automation features (e.g., auto-bidding, auto-budgeting, auto-creative suggestions). You need to measure the fe...
Collaborate with PM and Eng as DS
Question As a Data Scientist working with Product Managers and Engineers: 1. How do you structure collaboration (requirements, timelines, ownership)? ...
Design experiment for ads in chat with budgets
Context After launching an AI chat feature, the company wants to show ads inside the chat experience (you are interviewing for an Ads/Monetization dat...
Prioritize competing engineering requests
Scenario You are a Data Scientist/Analytics partner supporting multiple engineering teams. Two (or more) teams simultaneously ask you to prioritize th...
Design A/B test for AI chat box
Context A social platform (e.g., Reddit) plans to launch an AI chat box that answers user questions. The functionality overlaps with the existing Sear...
Implement a sliding-window rate limiter
Problem Design and implement an in-memory rate limiter using a sliding time window. You are given a stream of requests. Each request has: - key (e.g.,...
Design comment-likelihood prediction platform
Scenario You’re building an ML platform component that serves a model to predict the likelihood that a user will comment on a given post. The intervie...
Communicate and de-risk a non-experimental launch
Decision-to-Launch Plan After a Synthetic Control Result Context You are a data scientist who used a Synthetic Control method to estimate the causal i...
Justify synthetic control and handle inference
Synthetic Control: Assumptions, Estimation, Inference, and Diagnostics Context You are estimating the causal effect of an intervention on a single tre...
Design a causal evaluation without A/B testing
Non-Randomized Launch Decision via Synthetic Control: Complete Analysis Plan You need to make a go/no-go decision for a high-impact feature that canno...
Compute P(A>B) for m- and n-sided dice
Two fair dice are rolled independently: - Die A has m faces labeled \(1,2,\dots,m\). - Die B has n faces labeled \(1,2,\dots,n\). Each face is equally...
Query US-based users and most active forums
You are given user and post data for an online forum platform. Tables (schemas) Assume the following tables: users - user_id BIGINT (PK) - home_countr...
Design a feature store with CI/CD and reliability
System Design: Feature Store for Offline Training and Low‑Latency Online Inference Context You are designing a feature store to support machine learni...
Load and prepare JSON for modeling
Using Python in a Jupyter notebook, load a JSON dataset with fields: ( 1) hours spent reading A posts (float), ( 2) hours spent reading B posts (float...
Find word sequence with 1–2 char changes
Given a beginWord, an endWord, and a dictionary (wordList) of unique same-length lowercase words, determine whether there exists a transformation sequ...