Friday, March 6, 2026

I found Leetcode for System Design and its Awesome

I Found Codemia.io, Leetcode for System Design Interview, and It’s Awesome
credit- codemia.io

Hello guys, If you’re preparing for FAANG interviews, then you already know that Data Structures & Algorithms (DSA) and System Design are two key areas where you will be tested rigorously.

While LeetCode is the go-to platform for DSA, system design has always been a challenge — until now.

I recently found Codemia.io, and I must say, it feels like the LeetCode for System Design.

If you’ve struggled with structuring your system design answers, getting real feedback, or knowing whether your approach is correct, Codemia.io is a game-changer.

They not just have the biggest collection of System Design and OOP Design problem for practice they also have a free System deign course called Tackling System Design Interview Problems, which is a great free resource to learn essential System Design concepts.

It’s a short course with 2 hour of content but powerful and also have quizzes to test your skills. Here are all the key System deign topics you can learn on this free course:

Now, let’s checkout how Codemia.io can help you to prepare better for your System design and OOP Design interview and why I think its like Leetcode for System design.

Why System Design Needs a Platform Like Codemia.io?

Most system design resources today are long, text-heavy articles or expensive courses. The problem?

  1. No hands-on practice — Reading about system design isn’t enough; you need to actively design solutions.
  2. No structured progression — Unlike DSA, where problems are categorized by difficulty, system design prep often feels random and overwhelming.
  3. No evaluation or expert feedback — You don’t just need an answer; you need to know why one design is better than another.

This is where Codemia.io changes the game.

What Makes Codemia.io Special?

Instead of just giving you theory-heavy content, Codemia.io provides an interactive, structured, and guided approach to system design. Here’s what I loved:

1. Real-World System Design Problems

Codemia.io has over 120+ system design problems, each with a structured approach similar to how LeetCode presents DSA problems.

For example, consider the classic “Design a URL Shortening Service” problem.

You start with:
1. Functional and Non-Functional Requirements
2. Capacity Estimation
3. Database Schema and API Design
4. High-Level & Low-Level Design

It guides you step by step so you don’t feel lost.

Bonus: You also get access to a drawing board where you can sketch your architecture, just like in a real system design interview.

And most importantly they also share expert solution for most of the problems to see how an expert should answer that question. For example, here is the solution of how to design a URL shortening service and its also available for free

2. Difficulty-Based Categorization

Just like LeetCode, both System design and object oriented design problems are categorized as:

  • Easy — Foundational concepts like Load Balancing, Caching, Message Queues
  • Medium — Scenarios like Rate Limiting, Search Autocomplete, Real-Time Chat Systems
  • Hard — Complex designs like Distributed Databases, Cloud Storage, and Microservices Architecture

Each problem also includes company tags so you can focus on what’s asked at FAANG and other top tech companies. For example, this how to design Twitter problem is a medium scale problem which you can see to get some experience. It’s also free.

3. AI-Powered Hints & Evaluations

One of the best features is AI-assisted guidance. You get to chat with the coach — the AI agent which will help you with the question and solution.

1. If you get stuck, AI provides hints — just like LeetCode’s hint system.
2. If you submit a design proposal, AI evaluates it against industry best practices.
3. You get automated feedback on scalability, fault tolerance, and efficiency.

This bridges the gap between self-learning and expert mentorship.

Beyond System Design: Object-Oriented Design & AI Interviews

Codemia.io goes beyond just system design. It also covers Object-Oriented Design (OOD) Questions. If you don’t know , Object-Oriented Design is a common low-level design (LLD) round at FAANG.

Here are OOP problems you can solve on codemia.io to get some practice:

  • Classic problems like Parking Lot, ATM Machine, and Hotel Booking System
  • Step-by-step UML diagrams and class structure explanations
  • Comparison of different design patterns

If you struggle with OOD interviews, this is a goldmine.

Here is also all the OOP design problems available on Codemia.io

Codemia.io vs DesignGurus.io vs Educative

Now, let’s see how codemia.io compares with other popular resources we have used in past to prepare for System Design interview, notably DesignGurus.io whose Grokking the System Design Interview course is also one of my favorite and Educative.io, whose modern System design course is also a great resource.

You can see that codemia.io have highest number of practice problems, 120+ and growing, no other platform have that many questions which is also the big plus point of this platform and that’s why I called it “Leetcode of System Design”.

Second important point is expert written solution, also known as editorial solution in this website. There are mor than 80+ such solution which are great resource to compare your solution, learn from them and also find how to answer such questions.

What point to mention, what should you discuss, tradeoffs and so much more.

Another plus point of codemia.io is that it has object oriented programming questions which is not available in other courses, though DesignGurus.io have Grokking the Object Oriented Design Interview course which you can use for OOP design practice, but again when it comes to numbers, codemia.io wins.

So far we have compared the content but if we talk about platform, codemia.io have especially designed for online practice, particulary deisgn questions.

It comes with Interactive learning tools, interactive feedback and evaluation, chatbot and a great design tool for drawing. No other platform support so much feature which is essential to master system design.

Then there is community and you can also see the solution of other folks to learn from them. I love this feature as it allows me to see what other folks are thinking and how they solve that problem. This comparative analysis have helped me a lot to learn key system design concepts.

Overall, I think, codemia.io is a great platform to prepare for System design and OOP design interview. You may find courses but its hard to find a platform like this.

I highly recommend it for anyone preparing for System Design and Tech interviews. And, if you want to join now, you can also use discount code PROMOTION20 to get 20% off now.

Here is the link — 20% OFf on Codemia.io

Final words

If you’re preparing for FAANG system design interviews, Codemia.io is a must-try. It solves the biggest problems in system design prep:

  • Structured learning path (instead of random articles)
  • Real-world hands-on practice (instead of just reading)
  • Expert evaluation & AI feedback (so you know what to improve)
  • Mock interviews to simulate real conditions

I’m still exploring Codemia.io, but what I’ve seen so far is truly impressive.

If you’ve tried it, let me know what you liked or didn’t like.

Other System Design Articles and Resources you may like

Thanks for reading this article so far. If you like this article then please share with your friends and colleagues. If you have any questions feel free to ask in comments.

P. S. — They are also offering 20% discount now and you can get access for just $59 for one year, original price is $120 so you have a chance to save$60 and also learn System design better.

Master System Design Interviews Through Active Practice

Passively learning system design does not work. Now you can practice system design problems like the way you practice…

codemia.io

    By javin paul at March 06, 2026 0 comments
    Labels: Codemia.io , Coding Interviews , LeetCode , online resources , System Design

    20+ System Design Interview Problems for Experienced Developers to Practice Online

    Hello guys, if you’re preparing for system design interviews, one thing is clear: brushing up on basic concepts won’t cut it anymore.

    While its important to know System Basics like Caching, Replication, Rate limiting, API Gateway, Load Balancer, NoSQL vs SQL etc, today’s interviews are far more practical, and interviewers expect you to design real-world systems that are scalable, fault-tolerant, and performant.

    Whether you’re aiming for top tech companies like Google, Meta, Amazon — or up-and-coming AI startups — mastering system design is non-negotiable, even for senior developers.

    I know many friends who were confident enough to crack any System Design interviews and ignored prepreation due to their busy life, only to find that it was a struggle during interview.

    The good news? You don’t need to hunt around for scattered resources like articles, blogs, YouTube channels or Udemy courses.

    One platform that stands out for system design prep is Codemia.io, Leetcode for System Design.

    Codemia.io gives you:

    1. Real-world system design questions
    2. Clear explanations with free solutions for many problems
    3. A diagramming editor to practice like real interviews
    4. An ever-growing library curated by senior engineers
    5. Editorial solutions created by experts
    6. AI assisted learning and problem solving
    7. Expert evaluation

    All this makes Codemia.io a go-to resource for System Design interview prep and I have been using it for my interview preparation now.

    Earlier, I have talked about Is Codemia.io Good Place to Prepare for System Design? and in this post, I’ll share 20 must-solve system design problems, including free questions and solutions from Codemia.io that you should absolutely practice before your next interview.

    They have both free and paid questions and I am going to share them both for you.

    Top 5 Free System Design Interview Problems with Solutions

    These are completely free to access, and they include detailed editorials, diagrams, and architecture breakdowns on Codemia.

    1. Design a URL Shortening Service (Like TinyURL)

    In this problem you will learn to implement hash-based URL shortening, handle collisions, and manage redirection at scale.

    Here are both Functional and non-functional requirement

    Functional:

    1. Given a long URL, create an associated short URL.

    2. Given a short URL, return the associated long URL.

    Non-Functional:

    1. Availability — This service has to be highly available. Especially functionality (2) (redirection).
    2. Response time — Functionality (2) has to have low response time, e.g., less than 10ms. Functionality (1) (creating short URL) can takes more time — less than 10 seconds.
    3. Scalability — We will get more and more requests to create short URLs, so the storage has to be highly scalable.

    By the way, you should keep the requirements scope small. You only have 35–50 min in an interview. If you have a lot of requirements, you’d risk running out of time.

    We could add other requirements like custom link. But we will start with a small set of requirements. Easier to expand later than shrink.]

    You an further see the 📘 Solution once you have tried it yourself.

    2. Design Twitter

    In this problem you will design a messaging app like X with Follow/unfollow logic, timeline generation, tweet distribution, and fanout strategies explained.

    Here are detailed functional and non-functional requirements for you:

    Functional:

    1. User can tweet (send) up to 140 character message.
    2. User can follow other users.
    3. User can like other users’ tweets.
    4. User’s home feed will show tweets from the users they are following.

    The home feed will show top K popular tweets, based on the number of likes they receive, and the number of the followers the author has.

    Non-Functional:

    1. Scalability. It will have to serve a very large population, e.g., 500M DAU.
    2. Response time. User has to see tweets quickly. When user opens home feed, the first 10 tweets should show up within 500ms.
    3. Availability.

    See the 📘 Solution once you have tried your hand.

    3. Design Ticketmaster

    This is a great System design problem to learn Concurrency handling, seat locking, and avoiding double bookings.

    Here are the detailed functional and non-functional requirements:

    Functional:

    User is able to:

    1. Search for a theater by city or ZIP code.
    2. After selecting a theater, search for movies shown the the theater.
    3. After selecting a movie, select which show (e.g. show starting at 1PM, 3PM, 5PM, …)
    4. After selecting a show, user is presented a list of available seats.
    5. User can select the seats and finalize the booking.

    Non-Functional:

    We focus on the following aspects, as they are the most important:

    1. Consistency — once a booking is made, it has to be respected. No double bookings.
    2. Concurrency — multiple users are interacting with the service to view seats and book seats. Make sure system handles concurrent accesses and provide consistent bookings.
    3. Scalability
    4. Fault Tolerance

    You can also refer the 📘 Solution once you have tried your hand.

    4. Design a Parking Lot System

    This is another free System Design problem on Codemia.io where you would design using Object-Oriented Design and handle both functional and non-functional requirement like

    Functional:

    1. User can reserve a parking spot.
    2. User pays for the reservation.
    3. User can park a car on the parking spot.
    4. User can leave before the reservation time expires.
    5. One common error case to handle is when a user makes a reservation, but fails to show up. In this case, we would charge for the first 24 hours..

    Non-Functional:

    1. Scalability. We are designing this for an international company who has 1000s of parking lots across nations.
    2. Availability.
    3. Consistency. Once a reservation is made, the parking spot must be available for the user. No double-booking.

    Once you have tried it yourself you can also see the 📘 Solution here

    Top 10 Hard System Design Problems for Interviews (Paid)

    While these are paid on Codemia, they are worth every penny if you’re serious about mastering advanced system design.

    5. Design Facebook Messenger

    This problem is about designing a real-time chat, message delivery, synchronization across devices, and storage optimization.

    Functional Requirements:

    • Send/receive real-time text messages between users
    • Support group chats with multiple participants
    • Deliver messages across multiple devices with synchronization

    Non-Functional Requirements:

    • Message delivery latency < 100ms for real-time experience
    • 99.9% uptime to ensure reliable communication
    • Support 1 billion+ concurrent users with horizontal scaling

    6. Design a Resource Allocation Service

    This System design problem is perfect for scheduling systems like Uber, Lyft, or shared resource booking tools.

    Functional Requirements:

    • Match available resources (drivers/vehicles) to user requests
    • Real-time tracking and status updates of resource location
    • Handle booking confirmations and cancellations

    Non-Functional Requirements:

    • Response time < 3 seconds for resource matching
    • 99.95% availability during peak hours
    • Scale to handle 100K+ concurrent booking requests

    7. Design a Fitness Tracking App

    As part of this question you need to propose solution which can track steps, integrate GPS, sync across devices.

    Functional Requirements:

    • Track daily steps, distance, and calories burned
    • GPS integration for route mapping and location tracking
    • Sync fitness data across mobile, web, and wearable devices

    Non-Functional Requirements:

    • Battery optimization — minimal impact on device battery life
    • Data accuracy within 95% for step counting and GPS tracking
    • Offline capability — function without internet connectivity

    8. Design a Weather Reporting System

    Ingest and distribute real-time sensor data, cache weather forecasts, and scale APIs.

    Functional Requirements:

    • Ingest real-time weather data from multiple sensor sources
    • Provide weather forecasts and current conditions via API
    • Cache and serve weather data for millions of locations

    Non-Functional Requirements:

    • Data freshness — weather updates within 5 minutes of sensor reading
    • API response time < 200ms for weather queries
    • 99.99% availability for critical weather services

    9. Design Pastebin

    This System design problem can teach you about expiration logic, storing snippets, short link redirection.

    Functional Requirements:

    • Store and retrieve text snippets with unique URLs
    • Support automatic expiration of pastes after specified time
    • Generate short, shareable links for easy access

    Non-Functional Requirements:

    • Handle 1M+ paste creations per day
    • Data durability — 99.999% reliability for stored pastes
    • Low storage cost through compression and efficient data structures

    10. Design a Nested Comments System

    When you are asked this problem on interview, focus on tree structures, pagination, and moderation workflows.

    Functional Requirements:

    • Support hierarchical comment threads with unlimited nesting
    • Paginate comments for performance on large threads
    • Implement comment moderation and spam filtering

    Non-Functional Requirements:

    • Load comment trees in < 300ms for good user experience
    • Support 10K+ comments per thread without performance degradation
    • Scalable architecture to handle viral content with millions of comments

    11. Design Online Presence Indicator

    Track real-time status updates, efficient updates via websockets, and availability caching.

    Functional Requirements:

    • Track and display real-time user online/offline status
    • Update presence across all user sessions and devices
    • Provide last-seen timestamps for offline users

    Non-Functional Requirements:

    • Status updates propagated within 1–2 seconds via WebSockets
    • Minimize bandwidth usage for presence updates
    • 99.9% accuracy in presence detection

    12. Design a Vending Machine System

    This problem was asked to me on J P Morgan interview and its about Inventory management, embedded system integration, payment gateway design.

    Functional Requirements:

    • Track inventory levels and product availability
    • Process payments through multiple methods (cash, card, mobile)
    • Dispense products and provide change/receipts

    Non-Functional Requirements:

    • 99.9% uptime for payment processing
    • Real-time inventory synchronization across all machines
    • Secure payment processing with PCI compliance

    13. Design a Tagging Service

    Design a solution which support Tag hierarchy, search performance, and recommendation systems.

    Functional Requirements:

    • Create hierarchical tag structures and relationships
    • Support fast tag-based search and filtering
    • Generate personalized tag recommendations

    Non-Functional Requirements:

    • Search response time < 100ms for tag queries
    • Support billions of tags with efficient indexing
    • Auto-complete suggestions within 50ms

    14. Design Craigslist

    Design a Craiglist like system which can categorized listings, search index, and ad posting flows.

    Functional Requirements:

    • Post classified ads in categorized sections
    • Search and filter listings by location, category, price
    • Support user communication through anonymous email relay

    Non-Functional Requirements:

    • Handle 50M+ listings with fast search performance
    • 99.5% uptime for ad posting and browsing
    • Search results returned within 500ms

    15. Design Multi-Device Screenshot Capture System

    You need to design a solution where you can manage screenshots from remote devices, sync, and store them securely.

    Functional Requirements:

    • Capture screenshots from remote devices on-demand
    • Sync and store screenshots across cloud storage
    • Provide secure access controls for screenshot viewing

    Non-Functional Requirements:

    • Screenshot capture latency < 5 seconds
    • Secure transmission with end-to-end encryption
    • Support 1000+ concurrent device connections

    16. Design a Network Path Analyzer

    Design a System to track, simulate, and monitor multi-hop network paths.

    Functional Requirements:

    • Trace and analyze multi-hop network paths between endpoints
    • Simulate network conditions and monitor path performance
    • Generate network topology visualizations

    Non-Functional Requirements:

    • Real-time path analysis with < 100ms latency
    • Support monitoring 10K+ network paths simultaneously
    • 99.9% accuracy in path detection and metrics

    17. Design an Employee Swap System

    You need to design a system like a job board within your org — matching roles with available employees.

    Functional Requirements:

    • Match employees with available positions based on skills
    • Handle swap requests and approval workflows
    • Maintain employee profiles and role requirements

    Non-Functional Requirements:

    • Matching algorithm response time < 2 seconds
    • Support 100K+ employee profiles with efficient search
    • 99.5% system availability during business hours

    18. Design a Conference Room Booking System

    Can you design a system with calendar integration, booking slots, room conflicts, and availability display.

    Functional Requirements:

    • Book meeting rooms with time slot management
    • Integrate with calendar systems (Outlook, Google Calendar)
    • Handle booking conflicts and room availability checks

    Non-Functional Requirements:

    • Booking confirmation within 1 second
    • 99.9% accuracy in conflict detection
    • Support 1000+ concurrent booking requests

    19. Design a Video View Count System

    You need to design a system to optimize counting at high scale, prevent fraudulent views, aggregate with accuracy.

    Functional Requirements:

    • Count and aggregate video views in real-time
    • Detect and prevent fraudulent/bot views
    • Provide view analytics and reporting dashboards

    Non-Functional Requirements:

    • Handle 1M+ views per second with accurate counting
    • 99.99% data consistency for view counts
    • Anti-fraud detection with < 1% false positive rate

    20. Design an API Rate Limiter

    Design a System to implement sliding window or token bucket algorithm at scale for rate-limiting APIs.

    Functional Requirements:

    • Implement rate limiting using sliding window or token bucket algorithms
    • Support per-user, per-API, and global rate limits
    • Provide rate limit status and remaining quota information

    Non-Functional Requirements:

    • Rate limiting decision in < 1ms
    • 99.99% availability for rate limiting service
    • Scale to handle 1M+ API requests per second

    21. Design a Resource Management System (OOD)✨ Bonus

    This one is anObject-Oriented Design problem to prepare for FAANG and tier-1 companies. Includes class diagram practice.

    Functional Requirements:

    • Allocate and deallocate system resources (CPU, memory, storage)
    • Track resource usage and availability in real-time
    • Implement resource scheduling and priority management

    Non-Functional Requirements:

    • Resource allocation latency < 10ms
    • Support 10K+ concurrent resource requests
    • 99.99% accuracy in resource tracking and allocation

    Why Codemia.io Is My Go-To System Design Interview Prep Platform?

    I have read books, tried many courses and while all of them provide value the most value I have got from practicing the problem my myself and using AI for assistant.

    Also most platforms just give you a PDF solution or a video. But Codemia.io gives you:

    1. Real-world, open-ended problems
    2. Rich editorials with diagrams and best practices
    3. A built-in diagramming tool to practice visually
    4. Discussion board, solution submissions, and design patterns
    5. AI Assistance on both problem solving and evolution.

    Whether you’re a beginner or preparing for Staff Engineer interviews, Codemia.io has questions from simple CRUD systems to large-scale distributed architectures.

    They also have this nice System Design roadmap where you can click the topic and practice the related System Design problems

    For example, when you click Artificial Intelligence you can see these problems to practice

    💡 Pro Tip: Start with the free problems + editorials. Once you’re comfortable, invest in the premium ones to tackle the more complex scenarios.

    Conclusion

    That’s all about Top 20 System Design Problem you can practice on Codemia.io, online to hone your software design skills. These questions also touch based different topics like handling load, handling concurrency etc.

    System Design isn’t just an interview topic anymore — it’s a must-have skill for modern software engineers. Nowadays, your ability to design scalable systems can determine whether you land that Staff Engineer, SDE III, or Senior Software Engineer role.

    With Codemia.io, you get a structured way to learn, free questions to practice, and a real-world environment to simulate interviews.

    So, bookmark this list, tackle one problem a week, and you’ll be amazed at how fast your system design confidence grows.

    Ready to get started? Check out Codemia.io System Design Library and pick your first problem today!

    Other System Design Articles and Resources you may like

    Thanks for reading this article so far. If you like this article then please share with your friends and colleagues. If you have any questions feel free to ask in comments.

    P. S. — They are also offering 20% discount now and you can get access for just $59 for one year, original price is $120 so you have a chance to save$60 and also learn System design better.

    Master System Design Interviews Through Active Practice

    Passively learning system design does not work. Now you can practice system design problems like the way you practice…

    codemia.io

      By javin paul at March 06, 2026 0 comments
      Labels: interview questions , System Design
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