Prep Notebook

Code · LLD machine coding

LLD machine coding

Low-level design problems built end to end in Java, the way a machine-coding round expects: requirements, clean entities, design patterns, thread safety and a runnable demo.

github.com/aayushi-kunwar13/sde2-code-practice ↗

PhonePe prep · 10

BookMyShow

37classes

Design the backend for booking movie tickets.

StrategyFactoryRepositoryLockingCustom exceptionsService layer

BookMyShow (v2)

10classes

Elevator System

14classes

Design a controller for N elevators in a building.

StrategyObserverState

File System

4classes

Model files and folders.

Notification System

19classes

Design a service that sends notifications to users over several channels.

ObserverFactoryCustom exceptionsService layerChannels

Notification System (v2)

14classes
ObserverFactoryService layerChannels

Parking Lot

11classes

Design a multi-floor parking lot.

Strategy

Rate Limiter

12classes

Design a rate limiter for an API.

StrategyCustom exceptions

Vending Machine

16classes

Design a vending machine.

StateCustom exceptionsService layer

Hackathon Platform (machine coding round)

23classes

Design a coding-contest platform.

StrategyRepositoryCustom exceptionsService layer

Problems · 3

Rate Limiter

4classes
Strategy

Snake and Ladder

4classes

URL Shortener

1class

Design a URL shortener.

Personal project · 3

Car Rental System

9classes

Search cars by make, model and dates; reserve, cancel, and pay. Overlapping reservations are rejected, and reservations are thread-safe.

SingletonStrategyConcurrentHashMapsynchronizedEnums

Chess Game

15classes

Two-player chess on the console: an 8×8 board, each piece validating its own moves, turn handling, and invalid-move errors.

Abstract class + polymorphismCustom exceptionsGame loopsynchronized move

Customer Issue Resolution System

Planned