Mar 9 · 24 min read · TLDR TLDR: A Movie Booking System (like BookMyShow) is an inventory management problem with an expiry: seats expire when the show starts. The core engineering challenge is preventing double-booking under concurrent user load with a 3-state seat mode...
Join discussionMar 9 · 19 min read · TLDR TLDR: A Parking Lot is the "Hello World" of Low-Level Design. It teaches Encapsulation (ParkingFloor hides its Min-Heap), Abstraction (PricingStrategy interface), Inheritance (BikeSpot/CompactSpot/LargeSpot extend ParkingSpot), and Polymorphism...
Join discussionMar 9 · 22 min read · TLDR TLDR: A URL Shortener maps long URLs to short IDs. The core challenge is generating a globally unique, short, collision-free ID at scale. We use Base62 encoding on auto-incrementing database IDs for deterministic, collision-free short codes. ...
Join discussionMar 9 · 28 min read · TLDR: This is the code companion to the Parking Lot System Design post. We implement the core classes (ParkingLot, ParkingSpot, Ticket) in Java, apply the Singleton, Factory, and Strategy patterns, and use a Min-Heap to find the nearest available spo...
Join discussionMar 9 · 23 min read · TLDR TLDR: An LRU (Least Recently Used) Cache evicts the item that hasn't been accessed the longest when it's full. The classic implementation combines a HashMap (O(1) lookup) with a Doubly Linked List (O(1) move-to-front) for overall O(1) get and p...
Join discussionFeb 20 · 19 min read · TLDR: Tic-Tac-Toe looks trivial — until the interviewer says "make it N×N with P players and pluggable winning rules." The key design decisions: a Board abstracted from piece identity, a Strategy Pattern for win conditions, and a Factory for player c...
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Feb 11 · 21 min read · TLDR: A ride-booking system (Uber/Lyft-style) needs three interleaved sub-systems: real-time driver location tracking (Observer Pattern), nearest-driver matching (geospatial query), and dynamic pricing (Strategy Pattern). Getting state transitions ri...
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Feb 11 · 11 min read · TLDR: The Strategy Pattern replaces giant if-else or switch blocks with a family of interchangeable algorithm classes. Each strategy is a self-contained unit that can be swapped at runtime without touching the client code. The result: Open/Closed Pri...
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Jan 27 · 13 min read · In software development, particularly object-oriented programming and design, object creation is a common task. And how you manage this process can impact your app's flexibility, scalability, and maintainability. Creational design patterns govern how...
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