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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.
- 9403
- Questions
- 546
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- 11
- Topics
- 8
- Languages
Showing 1111–1140 of 3640 results
- DoorDashHardData ScientistCalculate Order Request Metrics
This question evaluates SQL and data-manipulation competencies for computing order-level metrics, including aggregations, joins, windowed event sequencing, timestamp/timezone handling, and NULL-aware comparisons.
Data Manipulation (SQL/Python)Onsite - DoorDashHardSoftware EngineerCompare front-end state management approaches
DoorDash software-engineer onsite front-end question: compare Redux with modern state and data management approaches (Redux Toolkit/RTK Query, React Query, SWR, Zustand, Recoil, MobX, Context) and design an end-to-end strategy for a React SPA that needs offline viewing, pagination, optimistic updates, and error retries. It tests separating client UI state from server cache, caching/invalidation, performance, type safety, testing, and an incremental migration plan off Redux.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerCompute cart total with best promotion
This question evaluates numerical reasoning for monetary calculations, handling of multiple promotion types, precision and rounding considerations, and edge-case handling such as empty carts and clamping totals within the Coding & Algorithms domain.
Coding & AlgorithmsOnsite - DoorDashMediumSoftware EngineerCompute dasher pay from deliveries
This question evaluates competency in data manipulation, schema design and validation, time-based aggregation, pay-computation logic, and handling of edge cases using SQL or Python.
Data Manipulation (SQL/Python)Onsite - DoorDashMediumSoftware EngineerCompute dasher pay with peak-hour query
This question tests the ability to handle overlapping time intervals and perform weighted calculations based on time-based pay multipliers.
Coding & AlgorithmsOnsiteAlgorithmsIntervalsData Processing - DoorDashMediumSoftware EngineerCompute dasher payout from API data
This question evaluates a candidate's proficiency in data manipulation and transaction aggregation using SQL or Python, encompassing time-zone-aware timestamp handling, pagination, late or missing events, cancellations and negative adjustments, rounding rules, and itemized breakdowns.
Data Manipulation (SQL/Python)Onsite - DoorDashMediumSoftware EngineerCompute nearest-exit distances in a grid
Compute nearest-exit distances in a grid evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Coding & AlgorithmsOnsite - DoorDashMediumData ScientistCompute rolling cold-delivery rates with windows
This question evaluates proficiency with SQL window functions, time-based joins, event deduplication and business-rule implementation for computing rolling metrics over temporal windows.
Data Manipulation (SQL/Python)Onsite - DoorDashMediumSoftware EngineerDebug Round-Robin and Consistent-Hash Routing
This problem tests the ability to identify flaws in load balancing implementations by evaluating consistency, distribution, and edge-case handling in Round-Robin and Consistent Hashing logic.
Software Engineering FundamentalsOnsiteLoad-BalancingConsistent-HashingDistributed-Systems - DoorDashMediumSoftware EngineerDebug a Random Dasher Registry
Debug a random dasher registry backed by a dense array and an ID-to-index map. Repair empty and swap-delete edge cases, preserve representation invariants, narrow error handling, and extend the design for concurrency and slow dependencies.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerDebug a Round-Robin Load Balancer, Then Implement Consistent Hashing
Debug a round-robin load balancer that must keep strict rotation while servers are added and removed, then implement a consistent-hash ring that gives each key a stable server. It tests off-by-one and index-mutation bugs, thread safety, stable hashing, virtual nodes, lookup cost, and how many keys move on membership changes.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerDebug a driver assignment bug
This question evaluates debugging, root-cause analysis, unit/integration test design, observability, and system-resilience competencies within the Coding & Algorithms domain, emphasizing practical skills in reproducing failures, isolating defects, and implementing targeted fixes.
Coding & AlgorithmsOnsite - DoorDashMediumSoftware EngineerDebug and refactor a legacy module
This question evaluates debugging, refactoring, naming and exception handling, input validation, code structure, and concurrency-safety design skills within a legacy codebase, requiring both hands-on code changes and higher-level reasoning about immutability, confinement, synchronization, and concurrent data structures.
Coding & AlgorithmsOnsite - DoorDashHardSoftware EngineerDebug the Last-Element Random Allocation Case
Implement and test an O(1) randomized pool that avoids and deterministically tests against the classic self-swap regression when removing the tail element.
Software Engineering FundamentalsOnsiteHash TableDesignTesting - DoorDashMediumSoftware EngineerDebug using logs and allocate tasks
This question evaluates a candidate's skill in log-driven debugging, production incident investigation, and cross-functional task allocation, covering competencies such as structured and contextual logging, correlation identifiers, noise reduction, minimal reproducibility, feature-flagged isolation, triage coordination, hypothesis tracking, root-cause confirmation, regression prevention, and blameless postmortems. It is commonly asked to assess operational troubleshooting and teamwork under production uncertainty within the Coding & Algorithms category, testing practical application of debugging techniques alongside conceptual understanding of incident management and process-level coordination.
Coding & AlgorithmsOnsite - DoorDashHardData ScientistDecide and test a 20% discount strategy
This question tests the ability to design a controlled experiment to evaluate a promotional discount strategy, focusing on causality, profit optimization, and long-term customer value impact.
Analytics & ExperimentationOnsiteCausal InferenceExperimentationUplift Modeling - DoorDashHardData ScientistDecompose and optimize delivery operational costs
This question evaluates a data scientist's ability to decompose per-order operational costs, identify high-impact levers to reduce unit economics, and design rigorous experiments and monitoring for a two-sided delivery marketplace, testing competencies in cost modeling, causal inference, experimentation design, and product analytics.
Analytics & ExperimentationOnsite - DoorDashHardData ScientistDefine and compute retention and churn precisely
This question evaluates a Data Scientist's competency in statistical measurement of user retention and churn, covering cohort definition, activity rules, risk-set-aware retention and churn formulas, censoring and delayed conversion handling, and survival-analysis concepts like time-to-churn, hazard, and cumulative incidence.
Statistics & MathOnsite - DoorDashHardData ScientistDefine metrics for new market expansion success
This question tests the ability to design a comprehensive evaluation framework for entering a new geographic market by balancing growth, unit economics, and marketplace balance.
Analytics & ExperimentationOnsiteAnalyticsMarketplaceKPIs - DoorDashMediumSoftware EngineerDescribe your most impactful recent project
A DoorDash software-engineering onsite behavioral question asking you to walk through your most impactful recent project: the problem, your specific role, measurable impact, a key technical decision and its trade-offs, how you handled scaling and reliability, a risk or failure you hit, and what you'd do differently. Includes a structured STAR-plus-deep-dive framework and a worked real-time-dispatch example.
Behavioral & LeadershipOnsite - DoorDashMediumData ScientistDesign Experiments to Measure Promotion Scheduling Impact
This interview question evaluates metric design, causal reasoning, experiment setup, diagnostics, SQL/statistical checks, and recommendations in a realistic interview setting. A strong answer for Design Experiments to Measure Promotion Scheduling Impact states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Analytics & ExperimentationOnsite - DoorDashMediumSoftware EngineerDesign Food Ratings and Driver Payouts
This question evaluates system design competencies such as API design, data modeling and storage selection for aggregated 5-point ratings, handling user-generated posts and likes, service decomposition, consistency trade-offs, scalability, and designing a monthly batch payout pipeline for driver earnings.
System DesignOnsite - DoorDashMediumSoftware EngineerDesign Food-Item Reviews, Ratings, and Mutable Vote Counts
Design item reviews and votes with purchase eligibility, unique reviews, rating aggregates, reliable counters, pagination, and recoverable caching.
System DesignOnsite - DoorDashHardSoftware EngineerDesign a 3-day donation platform
This question evaluates competency in designing scalable, highly available payment-enabled distributed systems, including skills in traffic spike handling, idempotency and reconciliation, real-time totals and leaderboards, latency and throughput planning, and compliance/privacy considerations.
System DesignOnsite - DoorDashMediumSoftware EngineerDesign a Donation Service with Reliable Payment and Payout Tracking
Design donation collection and charity payouts with a PSP, idempotent state transitions, durable ledger records, asynchronous provider events, and reconciliation.
System DesignOnsite - DoorDashMediumSoftware EngineerDesign a Donation System for a Three-Day Fundraising Campaign
Design a donation system for a fundraising campaign that runs for exactly three days, where donors choose a charity, pay through a payment processor and see running totals. It tests payment idempotency and reconciliation, handling a time-boxed traffic burst, avoiding write hotspots on totals, and fraud protection.
System DesignOnsite - DoorDashMediumSoftware EngineerDesign a Durable DAG Workflow for Order Refunds
This problem tests the ability to architect a robust, fault-tolerant workflow engine capable of managing complex state transitions and ensuring transactional integrity in distributed systems.
Software Engineering FundamentalsOnsiteSystem DesignDistributed SystemsWorkflow Engine - DoorDashMediumSoftware EngineerDesign a Food Item Review and Customer Reward System for a Delivery App
A DoorDash system design prompt to build a food item review system for a delivery app that also rewards customers for reviewing. It tests product judgment on open questions, verified-purchase writes, cached rating aggregates, and designing a practical, abuse-resistant reward program with reliable crediting.
System DesignOnsite - DoorDashMediumSoftware EngineerDesign a Food Rating System
This problem tests your ability to design a distributed, read-heavy rating and review system that handles high concurrency and ensures data integrity.
System DesignOnsiteDistributed SystemsCachingAPI Design - DoorDashMediumSoftware EngineerDesign a Food Review Platform
Design a food review platform for discovery, ratings, review text, optional dish-level content, and trusted aggregates. Define entity and review contracts, search and read paths, moderation, abuse resistance, privacy, scaling, and operational recovery.
System DesignOnsite
DoorDash