PayPal Data Scientist Interview Questions
Master your tech interview with our curated database of real questions from top companies.
Identify Unsupervised Techniques for Detecting Fraudulent Transactions
Unsupervised Fraud Detection: Modeling and Evaluation Without Labels Scenario You receive millions of historical transactions with no fraud labels. Ma...
Clean and Analyze User Transactions with Python Functions
transactions +---------+---------------------+---------+ | user_id | trans_ts | amount | +---------+---------------------+---------+ | 11 ...
Master A/B Testing: Key Concepts and Methodologies Explained
A/B Testing and Causal Inference: Core Concepts and Practice Scenario You are a data scientist interviewing for a role working on an online product. Y...
Identify Users with Specific Page Visit Sequence
page_visits +------------+---------+---------+----------+ | date | user_id | page_id | ts | +------------+---------+---------+----------+ ...
Analyze Transactions for Risk and Implement Mitigation Strategies
Real-Time Payments Risk: Accept or Decline, With Immediate Mitigations Scenario Two new card transactions arrive, and you must decide in real time whe...
Identify Session with Maximum Overlapping Sessions Count
sessions | session_id | start_time | end_time | | 1 | 2023-01-01 09:00:00 | 2023-01-01 10:00:00 | | 2 | 2023-0...
Analyze Transactions and Classify by Amount in SQL
transactions +---------------+---------+--------+---------+---------------------+-----------------+ | transaction_id| user_id | amount | status | ts ...
Describe Leading Without Authority in Data Management
Behavioral & Leadership Interview — Data Scientist (Onsite) Context You will be assessed on cultural fit and how you operate in ambiguous, messy data ...
Implement sliding-window device anomaly
Streaming detection algorithm: Implement a function process_logins(stream) that consumes a time-ordered stream of login events (user_id, ts, device_id...
Influence policy with BI deliverables
BI/Fraud Stakeholder Case: Drive an Account Takeover (ATO) Policy Change in 90 Days You join the Chicago Fraud team as a Decision Scientist. The hirin...
Build a real-time ATO model
End-to-end ML Case: Real-time Detection of Venmo Account Takeover (ATO) at Authorization Context Design a real-time machine learning system that score...
Optimize thresholds under fraud costs
Cost-sensitive Thresholding for Fraud (ATO) Classifier Context You are evaluating a binary classifier for account takeover (ATO) fraud on a large vali...
Design an A/B for ATO rule
Experiment Design Case: Real-time ATO Rule for PayPal/Venmo Context: You are designing and analyzing an online experiment to estimate the net business...
Write SQL to flag Venmo ATO
SQL case: You are a Decision Scientist on Venmo’s Fraud (ATO) team. Using the schema and sample data below, write a single Standard SQL query that ret...
Design elevator scheduling algorithm
System Design: Single-Elevator Control for a 4-Stop Building Context You are designing the control policy for a single elevator serving four stops: Ba...
Detect credit-card transaction fraud
Credit-Card Fraud Detection: Decisions and System Design Context You are designing a real-time decisioning system for card transactions with strict la...
Write conditional aggregation SQL queries
Question Write an SQL query to compute the total amount for rows satisfying a condition, comparing approaches that use SUM(CASE WHEN … THEN … END) ver...
Calculate Probability of Heads in Coin Flip Experiment
Coin Flips: Counting and Binomial Probabilities Context Assume 10 independent flips of a fair coin (probability of heads p = 0.5 for each flip). Each ...
Analyze KPI Drop: Immediate Steps for Stakeholder Persuasion
Behavioral + Mini-Case: Persuading with Data and Responding to a KPI Drop Context You are a Data Scientist interviewing onsite for a role focused on p...
Calculate and Find Average Contacts and Sync Percentage
dw_peers +--------------+---------------+-------------+ | user_id | synced_contact| date_synced | +--------------+---------------+-------------+ ...