You are designing a test booking system that must handle thousands of users booking slots concurrently. Which design approach best ensures availability and prevents double bookings?

hard📝 Trade-off Q15 of 15

LLD - Design — Hotel Booking System

AShow all slots as available and accept bookings first come, first served

BAllow users to book without checks and fix conflicts later manually

CUse a single global lock for all bookings to serialize requests

DUse optimistic locking with retries and real-time slot availability updates

Step-by-Step Solution

Solution:

Step 1: Understand scalability needs
Thousands of users require a scalable approach that avoids bottlenecks.
Step 2: Evaluate locking strategies
Single global lock serializes all requests causing delays; manual fixes cause poor user experience.
Step 3: Choose optimistic locking with retries
This approach allows concurrent attempts, detects conflicts, retries, and updates availability promptly.
Final Answer:
Use optimistic locking with retries and real-time slot availability updates -> Option D
Quick Check:
Optimistic locking + updates = scalable concurrency [OK]

Quick Trick: Optimistic locking scales better than global locks [OK]

Common Mistakes:

Using global lock causes slow system
Ignoring concurrency leads to double bookings
Manual conflict fixes harm user experience

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You are designing a test booking system that must handle thousands of users booking slots concurrently. Which design approach best ensures availability and prevents double bookings?

Step 1: Understand scalability needs

Step 2: Evaluate locking strategies

Step 3: Choose optimistic locking with retries

Final Answer:

Quick Check:

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