🏢 PhonePe Machine Coding Round – SDE Interview Experience

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

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