[Solved] Given this simplified booking code:def book_slot(slot_id): if is_available(slot_id): reserve(slot_id) return 'Booked' else:... | LLD

LLD - Design — Hotel Booking System

Given this simplified booking code:

def book_slot(slot_id):
    if is_available(slot_id):
        reserve(slot_id)
        return 'Booked'
    else:
        return 'Unavailable'

What happens if two users call book_slot for the same slot at the same time?

ABoth users get 'Unavailable' always

BBoth users get 'Booked' because reserve is atomic

COne user gets 'Booked', the other gets 'Unavailable' if reserve locks properly

DThe system crashes due to race condition

Step-by-Step Solution

Solution:

Step 1: Understand race condition in concurrent booking
Two users checking availability simultaneously can cause conflicts.
Step 2: Analyze reserve locking effect
If reserve locks the slot properly, first user books, second sees unavailable.
Final Answer:
One user gets 'Booked', the other gets 'Unavailable' if reserve locks properly -> Option C
Quick Check:
Proper locking = one booked, one unavailable [OK]

Quick Trick: Locking ensures only one booking succeeds [OK]

Common Mistakes:

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