Top System Design Interview Questions: Essential for Technical Interviews

System design interviews? They can feel like walking a tightrope. I’ve been on both sides of the table, and I’ve seen talented folks trip up, not because they lack skills, but because they weren’t ready for the system design deep dive.

Want to know how to nail system design interviews? Let’s get straight into it.

Why System Design Matters in Interviews

System design rounds aren’t just about knowing algorithms. They test your ability to think big, balance trade-offs, and build scalable systems. Companies want to see if you can:

Understand the big picture.
Design for scale.
Communicate clearly.

I remember one interview where the candidate designed a system that technically worked, but it would have crumbled under real-world traffic. That’s a red flag.

Question 1: Design a URL Shortener (like TinyURL)

This classic tests your grasp of:

Hashing.
Database design.
Scalability.

Here’s how I’d approach it:

Requirements: Clarify the scale (how many URLs per day?), desired features (custom URLs?), and constraints (latency?).
High-Level Design: Discuss using a hash function to generate short URLs and a database to store mappings.
Database Schema: Propose a simple table with columns for short URL, original URL, and creation timestamp.
Scaling: Suggest load balancing, caching, and database sharding.

Key takeaway: Don’t just focus on the core functionality. Think about how to handle millions of requests.

Question 2: Design a Rate Limiter

Essential for preventing abuse and ensuring system stability. You should cover:

Token bucket algorithm.
Leaky bucket algorithm.
Fixed window counters.

My approach would be:

Clarify Requirements: Define the rate limits (e.g., 100 requests per minute per user), scope (API endpoint, user ID), and actions (block, delay).
Algorithm Selection: Explain the trade-offs between different algorithms (e.g., token bucket is more flexible, fixed window is simpler).
Implementation: Describe how to store and update counters (e.g., Redis, Memcached).
Distributed Rate Limiting: Discuss using a centralized rate limiting service.

Internal Linking Opportunity: You can find similar scenarios in Coudo AI's machine coding problems.

Question 3: Design a Notification System

This tests your ability to handle asynchronous communication and fan-out patterns. Think about:

Message queues (e.g., RabbitMQ, Kafka).
Push vs. pull models.
Scalability and reliability.

Here's what you should consider:

Requirements: Types of notifications (email, SMS, push), delivery guarantees, and scale.
Architecture: Propose using a message queue to decouple the notification service from other components.
Fan-Out: Explain how to distribute notifications to multiple channels (e.g., using a publish-subscribe pattern).
Reliability: Discuss retries, dead-letter queues, and monitoring.

Keywords: Don't forget to mention Amazon MQ RabbitMQ if you have experience with those.

Question 4: Design a Search Autocomplete System

This tests your knowledge of:

Trie data structure.
Ranking algorithms.
Caching.

How to tackle it:

Requirements: Speed, accuracy, and relevance.
Data Structure: Explain using a Trie to store search terms and efficiently find prefixes.
Ranking: Discuss scoring suggestions based on frequency, popularity, and recency.
Caching: Suggest caching popular suggestions in a CDN.

Question 5: Design a Social Media Feed

A broad question that touches on many areas:

Database design.
Caching.
Consistency.

Break it down like this:

Requirements: Types of content, feed ordering (chronological, ranked), and scale.
Database: Discuss storing posts, user relationships, and likes/comments.
Feed Generation: Explain different approaches (push vs. pull) and their trade-offs.
Caching: Suggest caching feeds and individual posts.

Internal Linking Opportunity: For more examples, check out the Coudo AI problems.

FAQs

Q: How deep should I go into the technologies? You don't need to be an expert, but show you understand the basics and trade-offs.

Q: What if I don't know the answer? Be honest, but try to brainstorm possible solutions. Show your thought process.

Q: How important is code? System design interviews usually don't require coding, but you might sketch out key algorithms.

Wrapping Up

System design interviews are about demonstrating your ability to think critically, design for scale, and communicate clearly. Practice these questions, understand the underlying concepts, and you’ll be well-prepared.

If you're serious about mastering LLD, check out the Coudo AI learning platform. It’s a great way to get hands-on experience and refine your skills. These top system design interview questions are just the tip of the iceberg - keep learning, keep practicing, and you'll ace that interview.