Design a high-throughput Authentication System

Last updated: August 23, 2025

Quick Overview

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

Rippling
System Design
Software Engineer
Rippling
August 23, 2025
Software Engineer
Onsite
System Design
Hard

171

7

1,396 solved


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

Rippling asks this during the Onsite to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.

What the Interviewer Expects
  • Drive the design discussion proactively with minimal interviewer guidance
  • Perform detailed capacity estimation and use it to inform design decisions
  • Design for global scale with multi-region deployment and data consistency
  • Deep dive into 2-3 critical components with implementation-level detail
  • Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
  • Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
  • Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Requirements gathering and capacity estimation
Caching strategies (local, distributed, CDN)
Security and authentication
API design and rate limiting
Monitoring, logging, and alerting
Partitioning and sharding strategies
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How do you ensure data consistency across multiple services?
  • How would you handle a region-wide outage?
  • How would you implement rate limiting to protect the system?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For high-throughput Authentication System, key functional requirements in...

Capacity Estimation

Estimate the scale to drive design decisions. Assume 100M DAU with an average of 10 actions per user per day = 1B requests/day ~ 12K QPS average, ~36K...


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