[Solved] Given this booking function:def book(slot): lock(slot) if is_available(slot):... | LLD

LLD - Design — Hotel Booking System

Given this booking function:

def book(slot):
    lock(slot)
    if is_available(slot):
        confirm_booking(slot)
        unlock(slot)
        return 'Booked'
    unlock(slot)
    return 'Unavailable'

What is the main reason for locking the slot before checking availability?

ATo check slot availability without any restrictions

BTo speed up the booking process

CTo allow multiple users to book the slot concurrently

DTo prevent other users from booking the same slot simultaneously

Step-by-Step Solution

Solution:

Step 1: Understand Locking Purpose
Locking prevents concurrent modifications to the slot's availability.
Step 2: Prevent Race Conditions
Without locking, multiple users could see the slot as available and book it simultaneously.
Step 3: Ensure Consistency
Locking ensures only one booking can succeed at a time.
Final Answer:
To prevent other users from booking the same slot simultaneously -> Option D
Quick Check:
Locking prevents simultaneous bookings [OK]

Quick Trick: Lock before availability check to avoid conflicts [OK]

Common Mistakes:

MISTAKES

Assuming locking speeds up booking
Allowing concurrent bookings without locks
Locking after checking availability

Master "Design — Hotel Booking System" in LLD

9 interactive learning modes - each teaches the same concept differently

Learn Why Deep Arch Try Challenge Design Recall Scale

More LLD Quizzes

Given this booking function:

Step 1: Understand Locking Purpose

Step 2: Prevent Race Conditions

Step 3: Ensure Consistency

Final Answer:

Quick Check:

Want More Practice?