Design a large-scale Authentication Platform

Last updated: July 24, 2025

Quick Overview

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

Optiver
Software Engineering Fundamentals
Software Engineer
Optiver
July 24, 2025
Software Engineer
System Design Round
Software Engineering Fundamentals
Medium

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

This fundamentals question from Optiver's System Design Round tests whether you can reason about software design at a deep level. The interviewer expects discussion of maintainability, testability, and operational considerations.

What the Interviewer Expects
  • Apply engineering principles to a realistic design scenario
  • Discuss trade-offs between different approaches with concrete examples
  • Demonstrate understanding of testability, maintainability, and extensibility
  • Connect theoretical concepts to production engineering practices
  • Discuss how the approach scales with team and codebase size
Key Topics to Cover
Code review best practices
Testing strategies (unit, integration, e2e)
Performance optimization
CI/CD pipelines
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
  • What are the security implications of this design?
  • How would you document this for other engineers?
  • How would you handle backward compatibility?
  • How would this design change if the team size doubled?
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Sample Answer
Core Design Principles

For the design of a geo-distributed authentication platform at Optiver, we apply the principles of Separation of Concerns, Scalability, and Fault Tolerance.

  1. Separation of Concerns...
Architecture

The proposed architecture for the authentication platform is a Microservices Architecture leveraging a Distributed Database. Key components include:

  1. API Gateway: This serves as a singl...

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