Build a real-time Caching Pipeline

Last updated: August 5, 2025

Quick Overview

Design a real-time caching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Compass
System Design
Machine Learning Engineer
Compass
August 5, 2025
Machine Learning Engineer
System Design Round
System Design
Easy

61

6

4,488 solved


Design a real-time caching system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

This is a common system design question asked during System Design Round at Compass. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Compass values engineers who can think about scalability from day one.

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
Monitoring, logging, and alerting
Caching strategies (local, distributed, CDN)
Failure handling and fault tolerance
Consistency models and replication
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?
  • What would the deployment pipeline look like for this system?
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Sample Answer
Requirements
  • Functional Requirements:
    1. Provide a caching layer that can store frequently accessed data to reduce latency.
    2. Support real-time updates to cache when underlying data changes.
    3. ...
Capacity Estimation
  • Traffic Estimation:
    Assuming Compass has 10 million users, with each user making roughly 100 caching requests per day, the system needs to handle about 1 billion requests per day.
    • **Re...

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