Role: SDE-1
Platform: Onsite/Online (Coding Environment Provided)
Round Type: Machine Coding (Duration: 90–120 mins)
Language Used: Java

💼 Problem Statement:

Design a Fitness Class Booking System with the following features:

👥 User Management:

• Users can register/login with tier-based packages:

  • Platinum → 10 classes

  • Gold → 5 classes

  • Silver → 3 classes

📅 Class Management (Admin Functionality):

• Create, schedule, and cancel fitness classes (e.g., Yoga, Gym)

• Each class has a capacity and scheduled time

📌 Booking Functionality:

• Users can book classes based on available slots and their tier limit

• If the class is full → Add to waitlist

• On cancellation, the first waitlisted user gets the slot

❌ Cancellation:

• Users can cancel up to 30 minutes before the class

• Cancelled bookings restore user’s quota

🔄 Concurrency:

• Multiple users trying to book at the same time → Thread-safe booking logic was expected

🧠 My Approach:

• Used OOP Design: Classes like $User,FitnessClass,BookingService$, etc.

• Followed Separation of Concerns using service classes

• Stored everything in-memory using HashMaps/List (no DB required)

• Used $synchronized$ blocks for thread safety

• Hardcoded the main flow (register, create class, book, cancel, etc.) for quick testing

✅ Features Implemented:

✅User registration with package tiers

✅Admin can schedule classes

✅Class booking with capacity checks

✅Waitlist promotion after cancellation

✅Tier-wise booking limits

✅Concurrency-safe booking

💡 Tips for Candidates:

Think in **real-world object models**

Start with core functionality, leave enhancements for later

- Keep code modular and readable

Add **comments** to clarify assumptions and logic

Don’t forget edge cases (cancelling, waitlist promotion)

Feel free to ask if anyone wants the code or detailed breakdown. Hope this helps for your upcoming rounds! ✌️