Design a Secure Copilot API
Company: Microsoft
Role: Software Engineer
Category: System Design
Interview Round: Onsite
Design a secure API for an enterprise AI copilot product.
Assume the product serves multiple organizations, and authenticated users can send prompts, retrieve responses, and optionally access organization-specific tools or knowledge sources. The interviewer wants to focus heavily on security.
Discuss:
- The high-level API design and main components.
- How users and services should authenticate.
- How authorization should work across tenants, users, and tools.
- How access tokens should be issued, signed, validated, rotated, and revoked.
- How to prevent misuse such as prompt abuse, token theft, replay attacks, excessive usage, and cross-tenant data leakage.
- What additional security and reliability concerns appear as the system scales to a large number of requests.
Your design should address both normal product functionality and security-by-default.
Quick Answer: This question evaluates proficiency in designing secure, multi-tenant API systems with emphasis on authentication and authorization models, token lifecycle management, threat mitigation (such as replay attacks, token theft, and misuse), access control across tenants and tools, and scalability and reliability concerns.