Quick Overview

A coding problem about a cost-based rate limiter that processes ALLOW and RESET commands for many keys. Each key may spend a fixed budget per aligned time window and rejected requests record nothing, so it tests per-key window bookkeeping and 64-bit timestamp handling across up to 200,000 commands.

Per-Key Fixed-Window Cost Limiter with ALLOW and RESET Commands

Company: xAI

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

Overview: A coding problem about a cost-based rate limiter that processes ALLOW and RESET commands for many keys. Each key may spend a fixed budget per aligned time window and rejected requests record nothing, so it tests per-key window bookkeeping and 64-bit timestamp handling across up to 200,000 commands.

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