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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 2371–2400 of 9403 results
- CitadelMediumData ScientistStabilize LLM inference and estimate needed repeats
This question tests the ability to design an LLM inference pipeline that ensures result stability through statistical aggregation and estimates the minimum number of inference samples required to achieve a target confidence level.
ML System DesignTechnical ScreenLLMInferenceStatistics - CitadelMediumSoftware EngineerTop-K Largest Elements in Every Sliding Window
Design an algorithm to maintain and extract the top-K largest elements in descending order for each sliding window of size W across an array.
Coding & AlgorithmsTechnical ScreenSliding WindowHeapOrdered Set - CitadelMediumSoftware EngineerTwo-Player Terminal Battleship: Ship Placement From Input, Then Turn-Based Attacks
Build a two-player Battleship game as a class that runs in the terminal, with players taking turns to place ships by typing coordinates and sizes, then extend it so they can attack each other's fleets. It tests object modeling, input parsing and validation, turn handling, and delivering a large amount of working code under time pressure.
Software Engineering FundamentalsTechnical Screen - CitadelMediumData ScientistUpdate No-Intercept Regression Slopes Across Batches
Compute cumulative no-intercept regression slopes as paired data arrives in batches. Reuse running cross-products and sums of squares instead of refitting all historical rows.
Coding & AlgorithmsTechnical Screen - Citadel SecuritiesMediumSoftware EngineerDefine a Reliable Trade-Reconciliation Library Contract
Define trade-reconciliation contracts and OOP boundaries with exact values, timestamp tolerance, partial-fill questions, deterministic policy ownership, and traceable breaks.
Software Engineering FundamentalsTechnical Screen - Citadel SecuritiesMediumSoftware EngineerDesign a Top-Ten Trade Query with Exact Amounts
Design a top-ten trade query around an explicit ranking contract, exact monetary aggregation, bounded heaps, timestamp boundaries, and mutable-score streaming tradeoffs.
Software Engineering FundamentalsTechnical Screen - 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 - CitibankMediumData ScientistCompute expected payoff of reroll dice game
This question evaluates understanding of probability theory and expected-value computation in stopping-time processes, including conditioning and infinite-series reasoning, and also tests modeling of per-trial costs and break-even analysis.
Statistics & MathOnline Assessment - CitibankMediumData ScientistPrice options and bonds via binomial no-arbitrage
This question evaluates competence in no-arbitrage pricing, risk-neutral valuation, early-exercise features of American versus European options, and short-rate tree bond valuation within the Statistics & Math domain.
Statistics & MathOnline Assessment - ClickhouseMediumData EngineerAnswer SQL And Data Warehouse Fundamentals For A Data Engineering Interview
This problem tests foundational knowledge of SQL set operations, performance optimization techniques for join operations, and the architectural principles behind building scalable data warehouses.
Data Manipulation (SQL/Python)Technical ScreenSQLData WarehousingWindow Functions - 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 - ClioMediumSoftware EngineerGrowing the Managers Who Report to You and Handling Low Performers
A people-leadership behavioral prompt for an engineering role that manages other managers. Candidates describe how they grew a manager reporting to them and how they handled an underperformer, and are assessed on diagnosis, clear expectations, coaching, fairness, decisive outcomes and the context behind their decisions.
Behavioral & LeadershipOther - CloudKitchensMediumSoftware EngineerAnswer static and streaming Top-K queries
This question evaluates understanding of frequency counting, top-K selection, streaming and sliding-window algorithms and data-structure design in the Coding & Algorithms domain, testing both conceptual algorithmic reasoning and practical implementation skills.
Coding & AlgorithmsTechnical Screen - CloudKitchensMediumSoftware EngineerDesign a menu manager with enums
This question evaluates data modeling with enums, efficient data structure selection to meet specified time complexities, API design for CRUD operations, and practical implementation skills including a command-line interface and unit testing.
Coding & AlgorithmsTechnical Screen - CloudKitchensMediumSoftware EngineerDesign an in-memory cloud storage system
This problem tests your ability to design an efficient in-memory storage manager that handles concurrent file operations, user-based quotas, and data eviction policies.
Coding & AlgorithmsTechnical ScreenData StructuresSystem DesignOptimization - 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 - CloudKitchensMediumSoftware EngineerDesign receipt system with combo discounts
A CloudKitchens software-engineer technical screen: build a point-of-sale order that prints an itemized receipt on every item tap, then extend it to apply combo discounts. It tests cart data-structure design, receipt formatting, and the algorithm for selecting a valid set of non-overlapping combos.
Coding & AlgorithmsTechnical Screen - CloudKitchensMediumSoftware EngineerImplement concurrent order-accept/pickup simulator
This question evaluates concurrency and synchronization skills, including thread-safe design, inter-thread communication, state tracking, and correctness properties such as race-condition avoidance and deadlock freedom.
Coding & AlgorithmsTechnical Screen - CloudKitchensMediumSoftware EngineerImplement menu parser and serializer
This question evaluates proficiency in text parsing, hierarchical data modeling, tree construction and serialization, string manipulation, and algorithmic complexity (linear time/space).
Coding & AlgorithmsTechnical Screen - CloudTrucksMediumData ScientistCalculate Average Rate and Cumulative Jobs by State
This question evaluates competency in relational data manipulation and analytical SQL concepts—including joins, aggregation with DISTINCT counts, per-date averaging, rolling cumulative counts, and handling numeric edge cases—within the Data Manipulation (SQL/Python) domain for a data scientist role.
Data Manipulation (SQL/Python)Technical Screen - CloudflareEasySoftware EngineerDescribe contributions to production code
This question evaluates experience with production-quality software development, emphasizing contribution impact, code ownership, collaboration, and operational awareness.
Behavioral & LeadershipHR Screen - CloudflareMediumSoftware EngineerDesign an encrypted key-value store with login
This question evaluates a candidate's understanding of secure authentication, key management, and applied cryptography for encrypting data at rest within a user-scoped key–value store.
Software Engineering FundamentalsTechnical Screen - 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 - CloudflareEasySoftware EngineerExplain debugging methodology for production issues
This question evaluates a candidate's troubleshooting and incident-response skills, including root-cause analysis, systems-level reasoning, and prioritization under production constraints.
Software Engineering FundamentalsHR Screen
Citadel
Citadel Securities
Citi
Cloudflare