Architect a low-latency Authentication Engine

Last updated: March 7, 2026

Quick Overview

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

Shopify
System Design
Software Engineer
Shopify
March 7, 2026
Software Engineer
Onsite
System Design
Easy

106

14

916 solved


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

Shopify 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
  • Clearly define functional and non-functional requirements
  • Propose a reasonable high-level architecture with core components
  • Choose appropriate data storage solutions with basic justification
  • Discuss basic scaling strategies (horizontal scaling, caching)
  • Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
API design and rate limiting
Load balancing and horizontal scaling
Message queues and async processing
Requirements gathering and capacity estimation
Caching strategies (local, distributed, CDN)
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 would you handle a 10x increase in traffic overnight?
  • How would you optimize costs as the system scales?
  • How would you handle a region-wide outage?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For low-latency Authentication Engine, key functional requirements includ...

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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