Thread-Safe Key Counter, Then Cross-Process

Problem Overview

Write a counter that returns how many times a key has been called so far. Then make it thread safe, and finally make it work when several applications on the same host call it. What the report gives One Citadel Securities report lists the round as three asks, in the…

• 2 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
• The rest of the problem statement — full requirements, constraints, and edge cases
• Approach and trade-offs — what passing candidates did, and the mistakes that sink people