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Software Engineer 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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- 11
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Showing 2011–2040 of 5874 results
- DoorDashMediumSoftware EngineerImplement dasher active-time calculator
This question evaluates competency in time-based event processing, pairing related events, computing durations using LocalDateTime and Duration APIs, and analyzing algorithmic time and space complexity.
Coding & AlgorithmsTechnical Screen - DoorDashMediumSoftware EngineerImplement image carousel with comments and upvotes
This question evaluates a candidate's ability to design scalable data structures and efficient algorithms for interactive features, including API design, pagination, and consistency/concurrency handling for upvotes and per-image comment threads.
Coding & AlgorithmsOnsite - DoorDashMediumSoftware EngineerImplement round-robin load balancer
This question evaluates a candidate's ability to implement a strict round-robin load balancer with O(1) average operations while handling concurrent nextServer and update calls, health-check-driven skipping, and failure scenarios, testing competencies in data structures, concurrent programming, and fault-tolerant system behavior.
Coding & AlgorithmsOnsite - DoorDashMediumSoftware EngineerImplement string matching with follow-up
A DoorDash software-engineer coding screen on string matching: implement firstIndex(T, P) in O(|T| + |P|) time and O(|P|) space using KMP, then handle follow-ups on naive vs KMP vs Rabin–Karp, Unicode and very long inputs, edge cases, wildcard ('?'/'*') matching, and simultaneous multi-pattern search via Aho–Corasick. Includes corrected, complete solutions and complexity trade-offs.
Coding & AlgorithmsTechnical Screen - DoorDashMediumSoftware EngineerImplement string-path file system operations
This question evaluates competency in designing data structures for hierarchical string-path file systems, including string parsing, stateful API semantics, validation logic, and efficient lookup/update operations.
Coding & AlgorithmsTechnical Screen - DoorDashMediumSoftware EngineerInvestigate High Memory Usage
This question evaluates incident-response and operational debugging skills, focusing on diagnosing high memory usage in a distributed microservice architecture that includes caching and third-party integrations.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerInvestigate a Surge of Incorrect-Delivery Complaints at Scale
Triage thousands of delivery complaints using rates, joined operational data, focused sampling, mitigation, and evidence of recovery.
Behavioral & LeadershipOnsite - DoorDashMediumSoftware EngineerMake Rider Addition and Dispatch Safe Under Concurrency
Make concurrent rider addition and dispatch safe with atomic availability-to-assignment transitions, idempotent adds, narrow locks, and explicit distributed-state limits.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerMake a Courier Pay Workflow Resilient to Downstream Failures
Tests your ability to implement an idempotent, fault-tolerant workflow engine that safely executes financial transactions against an unreliable downstream ledger.
Software Engineering FundamentalsTechnical ScreenDistributed SystemsIdempotencyAPI Design - DoorDashMediumSoftware EngineerOwn Production Incidents and Validate Large Pipeline Migrations
Plan scalable migration checks, detect silent zero-output failures, and define incident recovery and monitoring ownership without a separate QA team.
Software Engineering FundamentalsOnsite - DoorDashMediumSoftware EngineerPaying Dashers Reliably When the Payment Service Is Unavailable
A system design follow-up about paying delivery drivers when the downstream payment service is unavailable. It tests reasoning about timeouts with unknown outcomes, durable records of amounts owed, retries that must never double-pay, recovery after long outages, reconciliation, and what drivers and operators see while payouts are delayed.
System DesignTechnical Screen - DoorDashMediumSoftware EngineerPooled Rideshare Earnings With Concurrent Rides and Surge
Compute a pooled-ride driver's total earnings where each minute's pay scales with how many riders are currently in the car, and minutes inside non-overlapping surge windows pay double, testing sweep-line interval counting with exact half-open boundaries and 64-bit totals.
Coding & AlgorithmsTechnical Screensweep-lineintervalsarrays - DoorDashHardSoftware EngineerPresent Your Proudest Project
Tests your ability to articulate a high-impact technical project end-to-end, highlighting architectural ownership, difficult trade-offs, rollout execution, and quantifiable business impact.
Behavioral & LeadershipOnsiteBehavioralLeadershipSystem Design - DoorDashMediumSoftware EngineerProcess Orders Through a DAG with Completion and Timeout Refunds
Design order DAG execution with prerequisite state, atomic completion-versus-timeout decisions, idempotent refunds, durable recovery, and accurate status queries.
System DesignOnsite - DoorDashMediumSoftware EngineerProject Deep Dive: Technology Choices, Trade-offs, Hindsight and Working with PMs
A DoorDash project deep dive and hiring manager conversation about a project you are proud of. It probes why you chose your technologies, which alternatives and trade-offs you weighed, the challenges you faced, what you would change, and how you worked with other teams and product managers.
Behavioral & LeadershipOnsite - DoorDashMediumSoftware EngineerProtect SLA and Choose Storage
This question evaluates system design competencies in service reliability and storage architecture, focusing on SLA protection during upstream latency spikes and trade-offs in choosing in-memory caches (e.g., Redis), relational databases, or alternative storage for order and payment state.
System DesignTechnical Screen - DoorDashMediumSoftware EngineerRecover a Project That Has Gone Off Track
This question assesses a candidate's ability to demonstrate leadership, analytical rigor, and project management skills when facing technical or execution failures.
Behavioral & LeadershipTechnical ScreenLeadershipProject ManagementCommunication - DoorDashMediumSoftware EngineerResolve Disagreement, Use Feedback, and Grow Engineering Judgment
Discuss technical disagreement, constructive feedback, concrete growth practices, and how varied perspectives contribute to accountable team decisions.
Behavioral & LeadershipOnsite - DoorDashHardSoftware EngineerResolve a Workplace Conflict
Tests your ability to navigate high-stakes technical or cross-functional disagreements constructively using data, empathy, and active listening to achieve a durable outcome.
Behavioral & LeadershipOnsiteBehavioralLeadershipConflict Resolution - DoorDashMediumSoftware EngineerReview Constant-Time Random Courier Selection and Removal
Maintain dense map indices for uniform random selection and swap-with-last removal, including empty states, concurrency, and complexity checks.
Software Engineering FundamentalsOnsite - DoorDashHardSoftware EngineerScale the cache to a distributed system
This question evaluates a candidate's ability to design and scale a distributed caching system, testing competencies in sharding and consistent hashing, replication and consistency models, request routing, failure detection, cache invalidation, capacity planning, and operational trade-offs for high-throughput, low-latency workloads.
System DesignTechnical Screen - DoorDashMediumSoftware EngineerSelect the best dasher for an order
This problem evaluates algorithmic selection and geometric computation skills—filtering eligible dashers, calculating Euclidean distances, and applying deterministic tie-breaking—within the Coding & Algorithms domain at an implementation-level algorithmic abstraction.
Coding & AlgorithmsOnline Assessment - DoorDashMediumSoftware EngineerSimulate Constant-Time Random Courier Selection
Design a courier pool data structure that supports adding, removing, and uniformly selecting random courier IDs in average O(1) time.
Coding & AlgorithmsTechnical ScreenData StructuresHash TableArray - DoorDashMediumSoftware EngineerSolve BFS grid delivery routing
This question evaluates proficiency in grid-based graph traversal and shortest-path computation, along with complexity analysis and handling dynamic changes, assessing skills in algorithm design, graph algorithms, and data structures within the Coding & Algorithms domain.
Coding & AlgorithmsTechnical Screen - DoorDashMediumSoftware EngineerSolve string match and DashMart BFS
This question evaluates proficiency with string algorithms and pattern matching, assessing understanding of substring search complexity and algorithm selection within the algorithms and data structures domain, and is commonly asked to verify efficient low-level text-search implementation and time/space trade-off reasoning at a practical implementation level. The "Dash Mart" grid BFS evaluates graph traversal, state-space modeling, and shortest-path reasoning for multi-target collection tasks within graph algorithms and path-finding, and is commonly asked to measure competence in BFS-based search, state encoding and optimization strategies with a focus on practical algorithmic application and performance considerations.
Coding & AlgorithmsTechnical Screen - DoorDashMediumSoftware EngineerSolve tree distance and design file system
This interview question evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer for Solve tree distance and design file system states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.
Coding & AlgorithmsOnsite - DoorDashMediumSoftware EngineerTrack the First Unique Restaurant in a Stream
This problem tests your ability to maintain stream uniqueness using a combination of a hash map and a doubly linked list to ensure constant-time operations.
Coding & AlgorithmsOnsiteHash MapLinked ListDesign - DoorDashMediumSoftware EngineerValidate a Shopping Cart
Implement a shopping cart validation function that checks item availability, consolidates duplicate entries, verifies inventory levels, and ensures order minimums are satisfied.
Coding & AlgorithmsTechnical ScreenHash TableData ValidationBusiness Logic - DropboxMediumSoftware EngineerCompute worst-case guesses for adaptive hangman
This question evaluates algorithmic problem-solving, combinatorial reasoning, and adversarial information-theoretic thinking by requiring modeling of worst-case query strategies for adaptive letter-guessing.
Coding & AlgorithmsOnsite - DropboxMediumSoftware EngineerDescribe Your Most Complex Project
This question evaluates a candidate's communication, leadership, ownership, and problem-solving competencies, specifically probing technical depth in system architecture, trade-offs, collaboration, risk management, and measurable impact.
Behavioral & LeadershipOnsite
DoorDash
Dropbox