Design a To-Do List Service (CRUD, Auth, Rate Limiting, Caching & API Versioning)

Company: Microsoft

Role: Software Engineer

Category: System Design

Difficulty: medium

Interview Round: Technical Screen

Quick Answer: This system design question evaluates practical full-stack architectural thinking across REST API design, authentication, rate limiting, and caching in a multi-tenant SaaS context. It assesses whether an engineer can reason about operational concerns — data isolation, burst traffic, API versioning, and cache consistency — beyond basic CRUD implementation.