Low-Level Design Problems
OOP problems with design patterns, runnable code, and company tags. Built for PhonePe, Flipkart, Swiggy, Razorpay-style machine coding rounds.
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Problems
22 problemsBeginner
5 problemsParking Lot
Multi-floor lot with strategy-based pricing, vehicle assignment, and extensible fee models.~15 min read
Tic-Tac-Toe
Generalised N×N board with O(1) win detection, pluggable win rules, and Deque-based turns.~12 min read
Snake & Ladder
Turn-based game with configurable board, dice strategies, and multiple player support.~15 min read
Vending Machine
Idle → selection → payment → dispense as a State machine, with change calculation and inventory.~15 min read
Library Management
Fine strategies, reservation queue, member tiers, overdue tracking.~16 min read
Intermediate
12 problemsSplitwise
Expense splitting with multiple strategies (equal, exact, percentage), debt simplification.~15 min read
Music Player
Shuffle without repeats, play/pause, next/prev, history tracking. Fisher-Yates + Strategy + Observer.~15 min read
Multilevel Cache
LRU/LFU eviction, composition of cache levels, read-through and write-through patterns.~15 min read
URL Shortener
Base62 encoding with atomic counter, custom aliases, click tracking, expiration, and strategy-based encoding.~15 min read
Elevator System
Multi-car dispatch with SCAN/LOOK scheduling, direction state, and swappable dispatch strategy.~18 min read
Rate Limiter
Token bucket, sliding window, fixed window with strategy pattern. Thread-safe per-client limiting.~15 min read
Payment Wallet
P2P transfers, idempotency, atomic operations, ledger, overdraft prevention.~18 min read
Task Scheduler
Priority queue, thread pool, recurring tasks, delayed execution, cancellation.~15 min read
E-commerce Cart
Pricing strategies, coupons, stock validation, tax calculation, checkout flow.~18 min read
Delivery Slot Booking
Capacity management, waitlist FIFO promotion, conflict detection, cancellation.~15 min read
Queue Management
Token system with priority queue, multiple counters, assignment strategies, wait time estimation.~16 min read
File System
In-memory file system with mkdir, ls, touch, rm. Tree traversal, path resolution, and thread-safe operations.~18 min read
Advanced
5 problemsInventory Management
Multi-warehouse stock tracking with atomic transfers, thread-safe operations, and repository pattern.~15 min read
Order Management
Order lifecycle with state machine transitions, observer notifications, builder pattern, and atomic stock deduction.~18 min read
Restaurant Booking
Time-slot reservations with conflict detection, waitlist management, table assignment strategy, and concurrency control.~18 min read
Pub/Sub System (Mini-Kafka)
Topics, partitions, consumer groups, offset tracking, at-least-once delivery.~20 min read
Ride Matching Engine
Proximity matching, trip state machine, fare with surge pricing, driver lifecycle.~18 min read