LLD Case Studies
Machine-coding designs grouped by domain — games, booking, devices, apps, infrastructure.
24 machine-coding problems with class diagrams, code, and pattern-by-pattern walkthroughs. Pick a category or work straight through.
Games & Puzzles
Tic-Tac-Toe
O(1) win detection on N×N boards
Snake & Ladder
Round-robin loop with seeded dice
Chess
Polymorphic pieces, check detection, special moves
Booking & Reservation
Movie Booking
Concurrent seat holds with TTL expiry
Hotel Booking
Per-date inventory counters
Car Rental
Reservations + pricing + return inspection
Meeting Scheduler
Room conflicts, attendee conflicts, recurrence
Airline Management
Multi-leg itineraries, atomic seat reservation
Devices & Systems
Parking Lot
Multi-floor lot, pricing strategies, concurrency
Elevator System
SCAN/LOOK scheduling across multiple cars
Vending Machine
State pattern + change-making
ATM System
Banking authentication, transaction processing
Traffic Signal
Phase machine with pedestrian + emergency override
Apps & Services
Splitwise
Money in cents, split strategies, min-cash-flow settlement
Food Delivery
Order lifecycle + partner assignment
LinkedIn Connections
Bidirectional BFS for degree of separation
Stack Overflow
Posts, votes (toggle/switch), reputation
Online Shopping Cart
Atomic stock reservation + idempotent payment
Library Management
Catalog, loans, holds, late fees
Infrastructure
Logger Utility
Levels, appenders, async writes
LRU/LFU Cache
O(1) get/put with doubly-linked-list + map
Rate Limiter (LLD)
Token bucket, leaky bucket, sliding window
File System
In-memory FS with composite pattern
Inventory Management
Multi-warehouse stock with event sourcing
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