Design a large-scale Authentication Platform

Last updated: May 10, 2026

Quick Overview

Design a multi-tenant authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Google
Software Engineering Fundamentals
Software Engineer
Google
May 10, 2026
Software Engineer
System Design Round
Software Engineering Fundamentals
Hard

2

3

4,578 solved


Design a multi-tenant authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Software engineering fundamentals questions at Google test your understanding of core CS concepts and their practical application. This System Design Round question evaluates how you apply engineering principles to build maintainable, scalable software.

What the Interviewer Expects
  • Design a complex system component applying multiple engineering principles
  • Reason about system-level trade-offs: performance, reliability, developer experience
  • Discuss advanced patterns: event sourcing, CQRS, distributed transactions
  • Address cross-cutting concerns: observability, security, backward compatibility
  • Demonstrate depth in both theoretical foundations and practical implementation
Key Topics to Cover
Performance optimization
SOLID principles
Version control and branching strategies
Design patterns (Factory, Observer, Strategy, etc.)
API design and RESTful conventions
Concurrency and thread safety
How to Approach This
  1. Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
  2. Choose data structures based on access patterns, not familiarity.
  3. Prefer immutable data and message passing over shared mutable state for concurrency.
  4. Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
  • How would you handle backward compatibility?
  • What are the security implications of this design?
  • What testing strategy would you use for this component?
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Sample Answer
Core Principles

Start by identifying which engineering principles are most relevant: **SOLID Principles**: Single Responsibility (one reason to change), Open/Closed ...

Design Approach

**API Design**: Define clear interfaces before implementation. Use RESTful conventions for HTTP APIs. Version your APIs from the start. Return meaning...


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