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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 7351–7380 of 9403 results
- RobinhoodHardSoftware EngineerCount Unique Dependents in a Referral DAG
Count unique direct and transitive dependents in a DAG, preserving edge direction, ignoring unknown endpoints, and handling shared descendants without double-counting.
Coding & AlgorithmsOnsite - RobinhoodMediumBackend EngineerCount and Rank Words in a Paragraph
This problem tests string manipulation, hash map usage for frequency counting, and custom sorting logic for deterministic ordering.
Coding & AlgorithmsTechnical ScreenStringsHash MapSorting - RobinhoodMediumData ScientistCreate OHLC Aggregates from Tick Data in Python
This question evaluates a candidate's ability to perform time-series bucketing and OHLC aggregation from tick data, testing skills in data parsing, stateful aggregation, and handling missing-interval forward-filling; it falls under Data Manipulation (SQL/Python) and assesses practical application rather than purely conceptual understanding.
Data Manipulation (SQL/Python)Onsite - RobinhoodMediumBackend EngineerCritique a Recent Engineering Project and Explain What You Would Redo
Prepare a candid deep dive on a recent engineering project, including personal ownership, a consequential technical decision, and observed outcomes. Identify a real weakness, trace its cause, and explain what you would redesign today.
Behavioral & LeadershipTechnical Screen - RobinhoodMediumBackend EngineerDeep-Dive a Distributed Service Project
This question assesses a candidate's ability to articulate the architecture, constraints, and operational challenges of a distributed system they previously owned, while demonstrating clarity in personal impact and technical decision-making.
Behavioral & LeadershipTechnical ScreenSystem DesignDistributed SystemsCommunication - RobinhoodMediumSoftware EngineerDefend the Complexity and Scalability of a Project
Prepare a project deep dive that withstands repeated questions about technical difficulty and scalability. Define your ownership, defend a genuine trade-off with evidence, identify current bottlenecks, and propose incremental scaling only when measurable signals justify it.
Behavioral & LeadershipOnsite - RobinhoodMediumSoftware EngineerDefine and Calculate Employee Referral Counts
Implement an algorithm to compute direct and total downstream referral counts for every employee in a directed graph that may contain duplicates, converging paths, and cycles.
Software Engineering FundamentalsOnsiteGraphBFSDFS - RobinhoodMediumSoftware EngineerDesign Payment Processing with Idempotency and Reconciliation
Design a resilient payment processing system that interfaces with third-party payment gateways, guarantees exactly-once execution via idempotency, manages complex payment state machines, and resolves discrepancies via reconciliation.
System DesignOnsitePaymentsIdempotencyDistributed Systems - RobinhoodMediumData ScientistDesign Real-Time Analytics Pipeline with Kafka and Flink
This interview question evaluates behavioral evidence, ownership, communication, trade-offs, and measurable outcomes in a realistic interview setting. A strong answer for Design Real-Time Analytics Pipeline with Kafka and Flink states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Behavioral & LeadershipOnsite - RobinhoodMediumSoftware EngineerDesign a Cron Job Scheduler for 100K Jobs With At-Least-Once Execution
A system design question about a cron job scheduler that stores about 100,000 recurring job definitions, runs up to 10,000 jobs at once and guarantees at-least-once execution. It tests data modeling, including whether a schedule belongs on the job, finding and dispatching due jobs at scale, and failure handling with leases and retries.
System DesignOnsite - RobinhoodHardSoftware EngineerDesign a Distributed Scheduler with At-Most-Once Runs
Design a distributed scheduler around strict at-most-once run starts, durable identities, ambiguous crashes, SLA failures, queue recovery, logs, and notification outboxes.
System DesignOnsite - RobinhoodMediumSoftware EngineerDesign a Fault-Tolerant Distributed Job Scheduler
This question tests the ability to design a distributed, fault-tolerant system capable of scheduling and executing tasks reliably at scale, emphasizing durability, state management, and consistency.
System DesignOnsiteDistributed SystemsReliabilityTask Queues - RobinhoodMediumFrontend EngineerDesign a Photo Album App
This question evaluates proficiency in frontend system design, specifically client-side component and data architecture, state management and normalization, real-time synchronization, and large-media upload flows; it sits in the System Design domain with a Frontend Engineer focus and tests practical application of these competencies.
System DesignOnsite - RobinhoodMediumSoftware EngineerDesign a Photo Management Service
This question evaluates a candidate's ability to design scalable, reliable photo management systems, focusing on API design, storage architecture, metadata modeling, album management, and operational concerns for large numbers of users and photos.
System DesignOnsite - RobinhoodMediumSoftware EngineerDesign a Reliable Distributed Job Scheduler
This question tests the ability to design a distributed, fault-tolerant job scheduler capable of handling job lifecycle states, worker coordination, and consistent scheduling across multiple tenants.
System DesignTechnical ScreenDistributed SystemsSchedulingReliability - RobinhoodMediumSoftware EngineerDesign a Task Scheduler and Executor
Design a high-scale task scheduler for one-time, cron-like, fixed-rate, and fixed-delay execution. Cover versioned task and attempt states, due-time indexing, safe concurrent claims, retries, leases, backpressure, idempotency, recurrence semantics, and recovery.
System DesignOnsite - RobinhoodMediumSoftware EngineerDesign a constrained cache and secure string validator
This question tests the ability to implement a thread-safe, size-constrained cache (LRU-like) and robust string validation logic for identifying malformed or potentially malicious input strings.
Coding & AlgorithmsOnsiteConcurrencyLRUHashing - RobinhoodMediumSoftware EngineerDesign a distributed job scheduler
This question tests the ability to design a fault-tolerant, scalable distributed system capable of scheduling one-time and recurring background tasks with guaranteed execution semantics.
System DesignOnsiteDistributed SystemsScalabilityDatabase Design - RobinhoodEasySoftware EngineerDesign a distributed job scheduler service
This question evaluates understanding of distributed systems and microservice architecture, scheduling and timeout semantics, fault tolerance, scalability, and data modeling for job metadata, run history, and logs.
System DesignTechnical Screen - RobinhoodMediumSoftware EngineerDesign a job scheduler with SLA and logs
This question tests the ability to design a distributed, fault-tolerant job scheduling system capable of meeting strict SLAs and providing audit-ready logging.
System DesignTechnical ScreenDistributed SystemsTask QueuesScalability - RobinhoodMediumSoftware EngineerDesign a live and historical stock quote API fed by a redundant exchange trade feed
A system design question that asks for a stock quote API serving live prices at about 10 million requests per second and one-day, one-month and one-year history at about 1 million, fed by two redundant exchange trade connections. It tests sequence-number arbitration, gap replay, fan-out of live state, bar aggregation and caching at scale.
System DesignOnsite - RobinhoodMediumSoftware EngineerDesign a referral leaderboard with chain-based counts
This question evaluates a candidate's ability to model and compute transitive referral counts using graph-like structures and efficient data structures, testing skills in algorithm design, counting, and sorting within the Coding & Algorithms domain.
Coding & AlgorithmsOnsite - RobinhoodMediumSoftware EngineerDesign a secure trading app on AWS
This System Design question evaluates secure cloud-based architecture on AWS, covering competencies in authentication and authorization, PII handling and auditability, API and data model design, and scalable low-latency market-data retrieval.
System DesignTechnical Screen - RobinhoodMediumSoftware EngineerDesign an At-Most-Once Job Scheduler
This question tests the ability to design a distributed, fault-tolerant job scheduler that guarantees tasks are executed no more than once, focusing on state management and concurrency control.
System DesignOnsiteDistributed SystemsConcurrencyFault Tolerance - RobinhoodMediumSoftware EngineerDesign an Order Execution System for Market and Limit Orders with Cancellation
A system design question about building the order execution system for a retail brokerage, where users place market and limit orders and can cancel them. It tests order execution flow, order state transitions with partial fills and cancels, failure handling, tracking user balances, and scaling the design to millions of orders.
System DesignOnsite - RobinhoodEasyData ScientistDesign an experiment to launch fractional shares
This question evaluates a candidate's competency in experimentation design, product analytics, statistical power and sample-size calculation, causal inference, and risk identification within a brokerage product context.
Analytics & ExperimentationOnsite - RobinhoodEasySoftware EngineerDesign an iOS Timer App with Consistent State and Asynchronous UI Updates
Design an iOS timer around explicit state transitions, clock-based elapsed time, main-thread UI updates, callback ownership, and lifecycle behavior.
Software Engineering FundamentalsTechnical Screen - RobinhoodMediumSoftware EngineerDesign authorization and audit logging systems
This question tests your ability to design a scalable, low-latency authorization framework and a reliable, tamper-proof audit logging system for a financial platform.
System DesignOnsiteSecurityAuthorizationAudit Logging - RobinhoodEasySoftware EngineerDesign in-memory payment and friendship system
This question evaluates object-oriented design skills, stateful in-memory data structures, request processing, and correctness constraints such as friend relationships, unique request IDs, and atomic balance transfers.
Coding & AlgorithmsTechnical Screen - RobinhoodMediumData ScientistDiagnose Decline in First Day Funding Rate
Diagnose Decline in First Day Funding Rate evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Analytics & ExperimentationTechnical Screen
Robinhood