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Interview Questions
Practice 9403 coding, system design and machine learning questions from 546 companies, sorted by role, topic and interview round. Every question has step-by-step hints, a code runner that supports 8 languages and an AI mentor; members also get the full solution walkthrough.
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Showing 2761–2790 of 3640 results
- PayPalMediumSoftware EngineerMinimize a String Using Allowed Swaps
This question evaluates understanding of graph connectivity and constrained string reordering, along with proficiency in applying efficient data structures and algorithms for handling large inputs.
Coding & AlgorithmsOnsite - PayPalEasyData ScientistReduce airport ride cancellations under causal constraints
A PayPal Data Scientist onsite product-sense and causal-inference case: design a measurement framework, hypotheses, and experimentation strategy to reduce airport ride cancellations in a ride-hailing marketplace without harming marketplace health. It tests metric trees, interference-aware experiment design (switchback, partial-population, encouragement/IV), satisfaction proxies, confounder handling, and stakeholder communication.
Analytics & ExperimentationOnsite - PayPalMediumData ScientistResolve Conflicts in Data Science Leadership Scenarios
This interview question evaluates behavioral evidence, ownership, communication, trade-offs, and measurable outcomes in a realistic interview setting. A strong answer for Resolve Conflicts in Data Science Leadership Scenarios states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Behavioral & LeadershipOnsite - PayPalMediumMachine Learning EngineerSearch a word in a grid
This question evaluates proficiency in grid traversal and stateful search techniques such as depth-first search and backtracking, including visited-state management and pruning strategies within the Coding & Algorithms domain.
Coding & AlgorithmsOnsite - PayPalEasyData ScientistShould you play a dice payout game?
This question evaluates understanding of probability, expected value, and payoff-driven decision-making by requiring computation of expected return from discrete game outcomes. It is commonly asked to assess quantitative reasoning in the Statistics & Math category and primarily tests conceptual understanding of expected value and probabilistic reasoning rather than practical implementation.
Statistics & MathOnsite - PayPalMediumData ScientistWrite conditional aggregates with CASE WHEN
Write conditional aggregates with CASE WHEN evaluates SQL or pandas logic, joins, grouping, window functions, null handling, edge cases, and validation in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Data Manipulation (SQL/Python)Onsite - PayPalMediumData ScientistWrite conditional aggregation SQL queries
This question evaluates proficiency with conditional aggregation in SQL, including the use of SUM(CASE WHEN ...) versus filtering with WHERE and the implications of placing aggregation filters in HAVING for grouped queries, within the Data Manipulation (SQL/Python) domain.
Data Manipulation (SQL/Python)Onsite - PerplexityMediumSoftware EngineerDesign personalized discovery recommendations
This problem evaluates your ability to design a scalable, real-time recommendation system that balances personalization with content discovery in an information-seeking environment.
ML System DesignOnsiteRecommender SystemsML InfrastructureRanking - PerplexityMediumSoftware EngineerDesign trending queries ranking system
This question tests the ability to design a high-throughput, real-time pipeline that identifies and ranks trending search queries, requiring trade-offs between freshness, accuracy, and system latency.
ML System DesignOnsiteSystem DesignReal-time StreamingRanking - PerplexityHardSoftware EngineerIn-Memory File System: Strict mkdir, touch, ls, rm, rmdir and a Command Runner
A two-part coding exercise to build an in-memory file system: first mkdir, touch and ls with strict path validation and no implicit creation of parent directories, then rm, rmdir and a function that executes command sequences. It tests tree modeling, error handling and working against provided tests.
Software Engineering FundamentalsOnsite - PersistenceMediumSoftware EngineerExplain Lazy Loading and Frontend Code Splitting
This question tests your understanding of performance optimization techniques in large-scale frontend applications, specifically how to balance initial load time against runtime latency.
Software Engineering FundamentalsOnsiteFrontendPerformanceArchitecture - PersistenceMediumSoftware EngineerReason About Indexes, Kafka, and Database Locking
Tests practical database indexing, Kafka event ingestion with idempotency guarantees, and row-level locking strategies to prevent concurrency bugs and deadlocks in an inventory and order processing pipeline.
Software Engineering FundamentalsOnsiteDatabasesPostgreSQLKafka - PinterestHardSoftware EngineerAI-Assisted Coding: Add a Read-Through Cache for a Product GET API in an Existing Repo
In an AI-assisted coding round, add a read-through cache to an existing service so a product GET API calls ProductRepository less often, then explain the approach. It tests understanding a codebase before prompting, cache placement, expiry, invalidation and concurrency, and proving the change works.
Software Engineering FundamentalsOnsite - PinterestMediumData ScientistAnalyze Global Engagement and Impressions with SQL Queries
This question evaluates proficiency in SQL-based data manipulation and analytical querying, covering aggregation, grouping, ranking, and the correlation of impressions with user engagement and feature usage metrics.
Data Manipulation (SQL/Python)Onsite - PinterestHardData ScientistAnalyze a geo rollout and interpret charts
This question evaluates causal inference and product analytics competencies — specifically specification of causal estimands and difference-in-differences, segmented (interrupted) time-series regression, power and duration calculations, spillover and donor-pool diagnostics, and selection of guardrail metrics.
Analytics & ExperimentationOnsite - PinterestHardData ScientistAnalyze survey with gender imbalance
Analyze survey with gender imbalance evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Statistics & MathOnsite - PinterestHardSoftware EngineerBehavioral Deep Dive: Owned Project Metrics, Fast Decisions, Feedback, and Conflict
Tests an engineering candidate's end-to-end technical leadership, ownership mindset, quantitative impact tracking, decision-making velocity under uncertainty, and interpersonal maturity.
Behavioral & LeadershipOnsiteBehavioralLeadershipSystem Ownership - PinterestHardSoftware EngineerBehavioral Round: Success Metrics, Slow Teammates, Team Health, Feedback and Conflict
Prepare concise answers for a software engineer behavioral round covering how you defined a project's success metrics, leading and communicating with engineers, a slow teammate, good and poor teams, giving and receiving negative feedback, conflict, and your strongest quality. It tests specific, well-structured stories with clear ownership and measurable outcomes.
Behavioral & LeadershipOnsite - PinterestMediumSoftware EngineerBuild an emoji blaster animation on iOS
This question evaluates a developer's skills in iOS UI interaction, animation frameworks, event scheduling and concurrency, performance optimization, and designing testable application architecture.
Software Engineering FundamentalsOnsite - PinterestMediumData ScientistCalculate 95% Bootstrap Confidence Interval for Order Values
This question evaluates a data scientist's competence in statistical inference using bootstrap resampling, proficiency with numerical computing for large sample operations, and attention to performance optimization.
Coding & AlgorithmsOnsite - PinterestMediumData ScientistClean and Aggregate Transactions for Finance Dashboard
This question evaluates data cleaning and transformation competencies including pandas-based vectorized operations, categorical mapping and feature flagging, as well as aggregation and summarization of transactional data in the data manipulation (SQL/Python) domain.
Data Manipulation (SQL/Python)Onsite - PinterestMediumSoftware EngineerCompute reachable cells for a cleaning robot
This problem tests graph traversal techniques (BFS/DFS) on a 2D grid, focusing on efficient coordinate management and state representation when navigating obstacles.
Coding & AlgorithmsOnsiteBFSGraph Traversal2D Grid - PinterestHardData ScientistConnect Probability, Experiment Sizing, and Bootstrap Inference
Tests end-to-end statistical rigor across discrete probability modeling, sample size derivation for A/B testing, bootstrap confidence intervals for heavy-tailed engagement metrics, and translating conflicting inferential signals into product launch recommendations.
Statistics & MathOnsiteStatisticsExperimentationA/B Testing - PinterestHardSoftware EngineerCount Distinct Active Pins per Time Segment from Overlapping Interaction Logs
Process overlapping pin interaction logs to calculate the number of distinct active pins over continuous time segments. Tests interval merging, line sweep techniques, and boundary handling.
Coding & AlgorithmsOnsitesweep-lineintervalssorting - PinterestMediumSoftware EngineerCross-reference logs to flag spam numbers
This question evaluates proficiency with data structures (such as hash maps), parsing and deduplication, frequency counting, input validation, and analysis of time and space complexity.
Coding & AlgorithmsOnsite - PinterestHardData ScientistDecide if ad load is optimized
This question evaluates competency in analytics and experimentation, covering experiment design, metric and guardrail definition, causal inference, statistical testing, segmentation for heterogeneous effects, and balancing user experience versus monetization.
Analytics & ExperimentationOnsite - PinterestMediumData ScientistDecode and Explain Ambiguity in Compression Strings
This question evaluates parsing of compact count-value encodings, reasoning about ambiguous encodings, and combinatorial enumeration of all valid decodings.
Coding & AlgorithmsOnsite - PinterestMediumSoftware EngineerDeep-Dive Two Projects Through Technical Decisions
This question tests your ability to articulate technical depth, decision-making frameworks, and engineering maturity by comparing two complex projects under different constraints.
Behavioral & LeadershipOnsiteLeadershipSystem DesignTechnical Communication - PinterestHardData ScientistDemonstrate leadership with concrete STAR examples
This question evaluates leadership, stakeholder influence, metric-driven decision-making, ambiguity management, end-to-end analytical ownership, and resilience in a Data Scientist context, categorized under Behavioral & Leadership.
Behavioral & LeadershipOnsite - PinterestMediumMachine Learning EngineerDescribe a Failure or Mistake and Its Lasting Lesson
This question assesses your ability to reflect on professional shortcomings, demonstrate accountability, and translate failure into actionable growth for both yourself and your team.
Behavioral & LeadershipOnsiteBehavioralAccountabilityConflict Resolution
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