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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
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Showing 841–870 of 3640 results
- CitadelMediumSoftware EngineerHow do you handle conflict at work?
This question evaluates interpersonal skills such as conflict resolution, communication, accountability, and leadership by asking about a concrete disagreement with a teammate in a software engineering context.
Behavioral & LeadershipOnsite - CitadelMediumSoftware EngineerImplement array merge, round-robin scheduler, and trading simulator
This problem tests your ability to manipulate data structures efficiently, implement a fair process scheduler, and manage event-driven state transitions.
Coding & AlgorithmsOnsiteArraysQueuesHeaps - CitadelMediumSoftware EngineerImplement task queue with insert, delete, execute
This question evaluates a candidate's ability to design and implement efficient dynamic priority management, including priority ordering, insertion-order tie-breaking, and support for add, remove, and execute operations.
Coding & AlgorithmsOnsite - CitadelMediumSoftware EngineerPerform an External Merge Sort with a Heap
Implement an external merge sort simulation that partitions a data stream into memory-bounded sorted runs and merges them using a min-heap.
Coding & AlgorithmsOnsiteExternal SortHeapStreaming - CitadelMediumSoftware EngineerSimulate 2048 and pack board into uint64
This question evaluates proficiency in implementing deterministic game-state logic and compact binary representations, specifically array manipulation and merge semantics for 2048 slide operations plus bit-level packing/unpacking of 4-bit exponent fields.
Coding & AlgorithmsOnsite - CitadelHardData ScientistSolve Classic Probability Questions
This problem tests your ability to calculate the expected stopping time of a stochastic process and your proficiency with the linearity of expectation in the context of sequential probability.
Statistics & MathOnsiteProbabilityExpectationStochastic Processes - CitadelHardData ScientistSolve probability and expectation problems
This set of problems evaluates probabilistic reasoning and expectation skills across discrete and continuous settings, covering conditional probability with evolving information, convolution and distribution derivation, occupancy/collector problems, symmetry-based variance on manifolds, and sequential selection/optimal stopping.
Statistics & MathOnsite - CitadelHardData ScientistSort a nearly sorted array
This question evaluates algorithmic problem-solving skills, specifically understanding sorting under constrained inputs and rigorous time and space complexity analysis.
Coding & AlgorithmsOnsite - Citadel SecuritiesMediumSoftware EngineerDetect Currency Arbitrage and Return a Profitable Conversion Cycle
Given a list of currency conversion rates, determine whether an arbitrage opportunity exists and return a sequence of conversions that ends in the starting currency with more money than it began with. Tests graph modeling, cycle detection, reconstruction of the profitable sequence, and handling of floating-point precision.
Software Engineering FundamentalsOnsite - Citadel SecuritiesMediumSoftware EngineerThread-Safe Producer-Consumer Queue: Mutex, Then Spin Lock, Then Lock-Free
Implement a thread-safe producer-consumer queue in C++, first with a mutex, then with a spin lock, then as a lock-free design with explicit memory ordering. Tests the C++ memory model, contention and cache effects, blocking versus spinning, and where memory is allocated on the hot path.
Software Engineering FundamentalsOnsite - CitiMediumSoftware EngineerExplain OS and networking basics
This question evaluates a candidate's understanding of operating system and networking fundamentals, covering processes, threads and context switching, concurrency versus parallelism, TCP/UDP and flow versus congestion control, and the end-to-end web request and browser rendering pipeline.
System DesignOnsite - CitiMediumSoftware EngineerExplain data structure fundamentals
This question evaluates understanding of data structure fundamentals, specifically hash map internals (hashing, collision resolution strategies, load factor, and resizing), time complexity analysis for search/insert/delete, contrasts between arrays and linked lists for random access and insertion, and typical use cases and complexities for stacks versus queues. It is commonly asked in technical interviews to assess algorithmic thinking and the ability to reason about performance trade-offs and appropriate data structure selection; domain: Coding & Algorithms; level: tests both conceptual understanding and practical application.
Coding & AlgorithmsOnsite - CitiMediumSoftware EngineerSolve two logic brain teasers
This pair of puzzles evaluates logical deduction and optimization competencies—one testing information-theoretic reasoning with constrained ternary comparisons and the other testing sequencing and scheduling trade-offs for minimal total time—and belongs to the Cognitive Ability / Logic category.
Statistics & MathOnsite - CitiMediumSoftware EngineerWalk through resume and impact
This question evaluates a candidate's ability to communicate a coherent career narrative and demonstrate technical ownership, decision-making, trade-off analysis, and metrics-driven impact within a software engineering context, testing competencies in leadership, product sense, and measurable delivery under the Behavioral & Leadership category.
Behavioral & LeadershipOnsite - ClickupMediumSoftware EngineerDesign weekly comment digest
This question evaluates understanding of scalable system architecture, integration with external ML services, handling rate limits, reliable scheduling and delivery, data modeling for aggregation and deduplication, and fault-tolerant ranking under load.
System DesignOnsite - ClickupMediumSoftware EngineerProcess document edit events
This question evaluates implementing and manipulating a line-based document through sequential event processing, emphasizing array/list operations, string handling, and state management; it belongs to the Coding & Algorithms domain and tests data-structure and input-event processing competency.
Coding & AlgorithmsOnsite - CloudKitchensMediumSoftware EngineerDesign real-time kitchen order fulfillment system
This question evaluates a candidate's competency in designing real-time backend systems, emphasizing concurrency control, stateful resource allocation, time-sensitive freshness constraints, efficient eviction policies, and action logging.
System DesignOnsite - CloudflareMediumSoftware EngineerDesign an encrypted log collection system
This question tests the ability to design a distributed, high-throughput ingestion pipeline that ensures log confidentiality and integrity using encryption at rest and in transit.
System DesignOnsiteSecurityDistributed SystemsEncryption - CloudflareMediumSoftware EngineerImplement a rule-based rate limiter
Design and implement a multi-rule rate limiter that tracks client request quotas across matching path prefixes using a sliding time window.
Coding & AlgorithmsOnsitesliding-windowdata-structuresdesign - Cockroach LabsMediumSoftware EngineerPoint-in-Time Reads from a Timestamped Key-Value Store
Build a versioned key-value store whose reads return the value a key held at a given timestamp: the latest write at or before that time, or an empty string if there is none. Tests choosing a per-key data layout that keeps point-in-time lookups fast across up to 200,000 operations.
Coding & AlgorithmsOnsite - Cockroach LabsMediumSoftware EngineerPresent and Defend an End-to-End Project You Owned: Architecture, Choices, Challenges
A choose-your-own system design round: present a core project you owned end to end at a previous job, then defend its architecture, technology choices and hardest challenges under detailed probing. Tests depth of ownership, trade-off reasoning and the ability to move from a diagram to concrete mechanisms.
System DesignOnsite - CohereMediumFrontend EngineerBuild a Credit Card Form With Validation and Linked Input Fields
A front-end UI coding question: build a credit card form with card number, name, expiry and security code, where every field is validated and the fields are linked, so the detected card network changes formatting and security-code rules. It tests state design, caret-safe input formatting, error timing, accessibility and safe handling of card data.
Software Engineering FundamentalsOnsite - CohereMediumMachine Learning EngineerBuild an LLM-driven text-game agent
This question tests the ability to design a robust pipeline for an LLM-based agent interacting with a stateful environment, focusing on context management, output validation, and error recovery.
Software Engineering FundamentalsOnsiteLLMPrompt EngineeringSystem Design - CohereMediumMachine Learning EngineerDefend Your Own Research Paper: Experimental Setup, Practicality and Later Work
A research paper round where you present your own published paper to an interviewer who already knows it and questions its weaknesses. Prepare to judge whether the experimental setup was reasonable, whether the results are practical, and what the field has learned since publication, all with specific, honest self-critique.
Machine LearningOnsite - CohereMediumSoftware EngineerDelete One '5' From a Digit String to Get the Largest Number
Given a digit string containing at least one 5, delete exactly one 5 so the remaining string has the largest possible numeric value, keeping any leading zeros. This intern online-assessment problem tests reasoning about how each digit position affects a number and careful handling of repeated digits.
Coding & AlgorithmsOnsite - CohereMediumMachine Learning EngineerDesign How an LLM Detects Questions Beyond Its Training Cutoff and Says So
Design how a large language model recognizes questions that depend on information after its training cutoff and tells the user where its knowledge ends. The question tests data construction for calibrated abstention, prompt versus fine-tuning versus retrieval trade-offs, and evaluating both over-refusal and hallucination.
ML System DesignOnsite - CohereMediumMachine Learning EngineerDesign a Post-Training Pipeline to Improve a 7B Model's Coding for an Enterprise
Design an end-to-end post-training pipeline that improves a 7B language model's coding ability for an enterprise customer, covering data collection, SFT, RLHF, evaluation, serving and a production feedback loop. The question probes dataset construction, reward model choice and why RLHF is still needed when SFT can learn from preference data.
ML System DesignOnsite - CohereMediumFrontend EngineerDesign a Real-Time Comment System Front End With Optimistic Updates
Front-end system design for a real-time comment feed, centered on optimistic updates: a new comment is appended to the list before the backend confirms it, so the user can keep typing. It tests client state modeling, reconciliation with live echoes, failure and retry handling, ordering, reconnection and rendering performance.
System DesignOnsite - CohereMediumMachine Learning EngineerExplain LLM training, RL, and evaluation
This question tests your conceptual understanding of the end-to-end LLM lifecycle, specifically the transition from raw text pre-training to alignment and evaluation.
Machine LearningOnsiteLLMRLHFPPO - CohereMediumMachine Learning EngineerExplain Top-k and Top-p Decoding
This question tests your conceptual and mathematical understanding of Top-k and Top-p (nucleus) sampling, focusing on how they modify the output probability distribution of autoregressive language models to balance creativity and coherence.
Machine LearningOnsiteNLPGenerative AISampling
Citadel
Citadel Securities
Citi
Cloudflare
Cohere