I Gave More Than 50 Interviews in the Last 12 Months — Here Are Most Asked System Design Questions

Real System Design Interview Question and how to answer them.

credit — Designgurus.io

Over the past 12 months, I’ve interviewed for Software Engineer and Senior Software Engineers roles at top-tier companies — including FAANG, unicorn startups, and mid-sized tech firms.

While the coding rounds tested my problem solving and algorithmic thinking, the system design interviews were the true game changers.

If you’re preparing for a System Design round, here are few things you can learn from my experience

The questions are broad. The answers are open-ended. And there’s often no single “right” solution — only trade-offs.

That said, I noticed a clear pattern. Certain system design questions keep showing up — sometimes with different labels or features, but at the core, the challenge is the same.

By the way, if you are preparing for System design interviews and want to learn System Design in a limited time then you should checkout sites like Codemia.io, ByteByteGo, Design Guru, Exponent, Educative, Bugfree.ai, System Design School, and Udemy which have many great System design courses, practice questions and tutorials.

Here are the top 10 most frequently asked System Design interview questions — based on my experience from over 50 interviews:

1. Design a URL Shortener (like Bit.ly)

This question is popular on many startups and product based companies. It’s high chance that you have already solved this question but if you see question on interview, make sure you talk about:

• Database schema design

• Hashing and uniqueness

• Redirection logic

• Handling high traffic (read-heavy)

• Caching

Bonus points if you talk about:

• Expiry logic

• Custom aliases

• Analytics (e.g., number of clicks)

You can also draw an high level diagram like this to explain your answer better:

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2. Design an API Rate Limiter

Rate Limiter is one’s a favorite at investment banks, fintech and platform companies. In fact, this question was asked to me twice, both on an American Investment bank and a British bank.

Here are the key concepts you can mention when you were asked this question

Key concepts:

• Token bucket vs leaky bucket algorithms

• Redis-based implementation

• Sliding window counters

• Per-user vs per-IP rate limiting

It’s also good know to know about Rate limiting in general as its one of the essential Software components on modern architecture.

3. Design a Messaging System (like WhatsApp or Slack)

This is another common questions on Big Tech and FAANG or MAANG whatever you call them. In this question they check whether you are familiar with

• Real-time communication

• Message storage

• Group chats vs 1-on-1

• WebSocket or long polling

• Delivery guarantees (at-least-once vs exactly-once)

Don’t forget:

• How messages are synced across devices

• How offline messages are handled

Again, you can also draw a high level diagram to better explain your answer like this one

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4. Design a News Feed System (like Facebook, Twitter)

I have seen this question on many places, sometime they use photo based news feed and some time text based.

In this question they want to see:

• Fan-out on write vs fan-out on read

• Feed ranking (optional but impressive)

• Sharding users

• Caching strategies (Redis/Memcached)

• Push vs pull models

Mentioning these points while answering these question can really help you. You can also see this post for full solution

5. Design an E-Commerce System (Add to Cart, Order Placement)

This question was asked to me on Amazon interview. They literally asked me to design Amazon and it kicked off a nice discussion.

They wanted to see:

• Product catalog storage

• Shopping cart state (session vs persistent)

• Inventory management

• Payment integration

• Order history

If you see this question again, make sure to discuss:

• Transaction consistency (think: distributed transactions or eventual consistency)

• Use of message queues

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6. Design a Distributed Cache (like Redis or Memcached)

This question was asked to me on a wall street investment bank. Since they store a lot of static and market data and use an in-house cache, they wanted to know whether I understand the concepts behind caching or not.

They were interested in :

• Consistency and replication

• Cache invalidation

• LRU vs LFU eviction

• Write-through vs write-around

• CAP theorem trade-offs

So, if you ever get asked this question, make sure you mention above point carefully in your answer to score brownie points.

Here is a nice diagram from ByteByteGo which explains Distributed Cache

7. Design a File Storage System (like Dropbox or Google Drive)

This is another System Design question I have seen on multiple places. As part of this question they look out for:

• File chunking and deduplication

• Metadata storage

• Versioning

• Upload/download flow

• Syncing across devices

Extra points if you mention:

• How you’d store large files efficiently

• Use of CDN for performance

As always its not about the right or perfect solution but about knowing the concepts and tradeoff and showing that you are capable of making a decision based upon requirement.

8. Design a Notification System (Email, SMS, In-App)

This question is very popular at companies with B2C focus.

Here is what you can include while answering this question:

• Event-driven architecture

• Retry mechanism

• Multi-channel support

• Priority queues

You can also practice this question on Codemia.io, a Leetcode style platform for System design interview. In fact, you can find most of the System design question I have shared here on Codemia.io

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9. Design a YouTube-like Video Streaming Platform

This question was asked to me on a senior software engineer interview at one of the Big Tech companies.

Here is what you can talk about if you see this question on your interview

• Video upload and encoding pipeline

• CDN for video distribution

• Video metadata indexing

• Streaming protocols (HLS/DASH)

• Recommendation engine basics

Here is a nice diagram from ByteByteGo which shows the high level design of YouTube like system

10. Design a Ride-Sharing App (like Uber or Lyft)

This is another question which is asked to senior developers and tech lead interviews.

Here are key points you can mention as part of this question

• GPS tracking

• Matching algorithm (drivers ↔ riders)

• Real-time communication

• Surge pricing logic

• Location indexing (e.g., using QuadTrees or GeoHash)

This tests not only system components but also scalability, data consistency, and latency tolerance.

How to Prepare for System Design Interview?

After being grilled dozens of times, here’s what helped me the most:

• Master the fundamentals: Start with concepts like load balancers, caches, databases, queues, CAP theorem, consistency models, etc. Practicing on sites like Codemia.io or DesignGurus.io can also help.

• Learn by designing: Pick 1 system daily, and sketch the architecture. Use tools like draw.io, notebook, or whiteboards.

• Read system design books: I highly recommend Designing Data-Intensive Applications by Martin Kleppmann and System Design Interview — An insider’s guide by Alex xu (All three parts, including ML Design)

• Join a course or cohort: If you’re serious, structured guidance can 10x your prep. For online courses, I have used ByteByteGo and Educative’s System Design course.

• Practice mock interviews: Mock interviews have helped me a lot on finding where I am and also gaining the confidence and skills to discuss these questions. You can use platforms like DesignGurus.io, Exponent, and InterviewKickStart for mock interviews with FAANG experts

Also, here is a nice System Design cheat sheet from ByteByteGo to quickly revise the essential System design concepts

credit — ByteBytego

Final Thoughts

System Design interviews can be intimidating — not because the tech is impossible, but because the scope is wide.

But once you know the core concepts and the most common problems, you can walk into your next interview with confidence.

If you’re currently preparing, pick 2 questions above, sketch your design, and record yourself explaining it. Do that daily for a week, and you’ll be in a whole new league.

Good luck!

And if you want me to break down any of the above questions in detail — just drop a comment.

Other System Design Articles you may like

The 20 Concepts That Turned My System Design Nightmare into Success

Scaling to Millions: The Secret Behind NGINX's Concurrent Connection Handling

The SWE (Software Engineer) Interview Prep RoadMap

System Design Basics - Database Scaling

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