Architect a scalable Authentication Engine
Last updated: June 2, 2026
Quick Overview
Design a scalable authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Scale AI
June 2, 202611
4
206 solved
Design a scalable authentication system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Scale AI asks this during the Onsite to assess your depth in software engineering. They want to see understanding of design patterns, system architecture, and the trade-offs involved in different technical approaches.
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
How to Approach This
- Apply SOLID principles. Single Responsibility makes code testable, Open/Closed makes it extensible.
- Choose data structures based on access patterns, not familiarity.
- Prefer immutable data and message passing over shared mutable state for concurrency.
- Design APIs with RESTful conventions, versioning, meaningful errors, and pagination from day one.
Possible Follow-up Questions
- How would you document this for other engineers?
- What testing strategy would you use for this component?
- What are the security implications of this design?
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Core Design Principles
For the scalable Authentication Engine, the key design principles are:
- SOLID Principles: These guidelines help create a robust and maintainable system. For example, the Single Responsibility P...
Architectural Approach
The architecture for the Authentication Engine will be microservices-based to ensure scalability and maintainability. Key components include:
- API Gateway: Serves as the entry point for all aut...
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