Low-Level Design (LLD) / OOD
Interview Preparation Handbook
21 Problems, Full Depth · each covering requirements, class diagrams, design patterns, concurrency, scaling, trade-offs, and more.
1
Parking Lot
Intermediate → Advanced+Concurrency
2
LRU Cache
Intermediate
3
Rate Limiter
Intermediate → Advanced+Distributed
4
Splitwise (Expense Sharing)
Intermediate → Advanced
5
Ride-Sharing Service (Uber/Lyft)
Advanced
6
Logging Framework
Intermediate (Pattern Showcase)
7
Notification System
Intermediate → Advanced
8
Coffee Vending Machine
Beginner → Intermediate
9
File System
Intermediate → Advanced
10
Pub-Sub / Message Queue
Advanced + Concurrency
11
Elevator System
Intermediate → Advanced+Concurrency
12
Tic-Tac-Toe / Board Game Engine
Beginner → Intermediate (Pattern Showcase)
13
Chess Game
Intermediate → Advanced
14
ATM Machine
Intermediate
15
Library Management System
Intermediate
16
Hotel Reservation System
Intermediate → Advanced (Concurrency)
17
Movie Ticket Booking System
Advanced (Concurrency Showcase)
18
Restaurant / Food Delivery System
Intermediate → Advanced
19
E-commerce Shopping Cart & Checkout
Intermediate → Advanced
20
Chat Application (WhatsApp-style)
Advanced
21
Stock Brokerage System
Advanced (Concurrency & Consistency)