[Solved] This booking system code sometimes allows double booking:def book(slot): if check_availability(slot): confirm_booking(slot) update_availability(slot, False)What is the likely cause? | LLD

LLD - Design — Hotel Booking System

This booking system code sometimes allows double booking:

def book(slot):
    if check_availability(slot):
        confirm_booking(slot)
        update_availability(slot, False)

What is the likely cause?

AAvailability is updated before booking

BNo locking or atomic transaction around check and update

CBooking confirmation is missing

DSlot is never checked for availability

Step-by-Step Solution

Solution:

Step 1: Review booking steps
Availability is checked, then booking confirmed, then availability updated.
Step 2: Identify missing concurrency control
Without atomic operation or lock, two users can pass check before update, causing double booking.
Final Answer:
No locking or atomic transaction around check and update -> Option B
Quick Check:
Atomicity needed to prevent double booking [OK]

Quick Trick: Use atomic transactions for check and update [OK]

Common Mistakes:

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