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Workday·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say
May 2026

Summary

Workday system design round, just one question but it took up the whole session. Not the most grueling interview but it made me realize how little I'd thought about randomness as an actual engineering problem.

Questions Asked (1)

Q1

How would you design a Pseudo Random Number Generator (PRNG)?

System DesignTechnical Trade-offsAlgorithms & Data Structures
Author's notes

I started with linear congruential generators because that's the first thing I remembered from school, but then they pushed on distribution quality and seed management and I kind of ran out of steam.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the requirements: what quality, speed, and security properties are needed? Then outline a design that balances simplicity, performance, and statistical quality, and discuss trade-offs between different PRNG algorithms.

Pro tip: Mention that for most applications, a simple xorshift or PCG algorithm is sufficient, but for cryptographic purposes, a CSPRNG like ChaCha20 is necessary—showing awareness of context and avoiding over-engineering.

1. Clarify Requirements

Ask about the intended use: is it for simulations, games, or cryptography? Determine needed properties like period, speed, memory, and security.

2. Choose Algorithm Type

Select between linear congruential generators (LCGs), xorshift, PCG, or cryptographic PRNGs based on requirements. Explain why the chosen type fits.

3. Design Core Components

Define the state size, seeding mechanism, and output function. Ensure the state transition and output generation are efficient and avoid biases.

4. Evaluate Statistical Quality

Discuss how to test randomness (e.g., Diehard tests, TestU01) and ensure the generator passes them for the intended use.

5. Discuss Trade-offs and Extensions

Compare performance, memory, and security trade-offs. Mention possible improvements like jump-ahead or parallel streams.

Key Points to Mention

  • Seed initialization and entropy sources
  • Period length and state space size
  • Statistical randomness and bias avoidance
  • Performance and memory footprint
  • Security considerations (CSPRNG vs. non-crypto)
  • Reproducibility and thread safety

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.