Citadel Software Engineer Interview Questions
Preparing for Citadel Software Engineer interview questions means getting ready for a rigorous, fast-paced process that blends algorithmic rigor with production engineering expectations. Distinctive features include a strong emphasis on low-latency, production-quality code and the ability to reason about systems under real-world constraints; candidates often interview across both Citadel and Citadel Securities teams, so expect questions that probe algorithmic problem solving, systems design, concurrency, and performance optimization alongside behavioral and product-minded discussions. The process typically begins with an online assessment or screening call, followed by multiple 45–60 minute technical interviews (CoderPad/pair programming) and a leadership/team-fit conversation; total timeline is often four to eight weeks. For effective interview preparation, practice timed coding problems in your primary language, rehearse system-design scenarios with focus on trade‑offs, and review debugging and performance-tuning examples from your projects. Be ready to explain design decisions and measurable impact from your past work, and simulate remote CoderPad sessions so you’re comfortable thinking aloud while coding. Prioritize clarity, algorithmic correctness, and pragmatic choices that demonstrate you can deliver reliable systems in a high-stakes environment.

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Merge K timestamped lists with timestamp coalescing
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Determine order of alien alphabet
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How do you handle conflict at work?
Describe a time you had a conflict with a teammate (e.g., disagreement on technical direction, priorities, code quality, or ownership). Please cover: ...
Compute BBO and NBBO from order data
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Implement task queue with insert, delete, execute
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Implement array merge, round-robin scheduler, and trading simulator
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Implement an in-memory order book API
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Check whether a string is a palindrome
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Implement LRU/LFU cache with custom eviction
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Return nodes on a tree diameter path
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Design a low-latency trading system
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Find earliest common meeting slot
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Design a token manager with lazy expiration
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Solve two DS&A optimization problems
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Minimize changes for k-periodic palindrome
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Solve four algorithmic problems
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Explain career motivations and choices
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Describe current work and relocation willingness
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