Build Discount Coupon Engine | System Design

Welcome to Lecture 24 of the Ultimate Low-Level Design (LLD) Series by Coder Army!

fifth week for #lowleveldesign #systemdesign #8weeksLLdchallenge.

We are doing 8 weeks challenge and going to complete the whole course within the duration with quality content on Youtube. Let’s learn LLD like never before and attain advance level mastery on this subject.

In this deep-dive LLD tutorial, we’ll design and implement a full-featured Discount Coupon Engine in C++/Java then translate the same concepts into Java. You’ll see how to:

1. Define flexible discount rules with the Strategy Pattern (Flat, Percentage & Capped Percentage)
2. Wire up a dynamic chain of coupons using the *Chain of Responsibility*, so multiple offers can apply in sequence or stop when needed
3. Manage your strategies and coupons as Singletons for global, thread-safe access
4. Compose your system step-by-step: from individual Coupon classes to a central CouponManager that registers, lists, and applies discounts
5. Walk through a sample Cart to see original vs. final totals, and inspect which promotions fired

Whether you’re building a shopping cart, a subscription service, or any application that needs powerful promo-code logic, this LLD session gives you the patterns and code scaffolding to get started.


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Code and Notes: Github : https://github.com/adityatandon15/LLD

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00:00 Introduction
02:14 Requirements
06:54 Happy Flow
09:22 UML Design for Discount Coupon Engine
54:53 Final UML
56:58 Code for Coupon Discount Engine

#SystemDesign #LowLevelDesign #LLD #AdapterPattern #DesignPatterns #Cplusplus #JavaDevelopers #UMLDiagrams #TechInterviews #SoftwareEngineering #XMLtoJSON #CleanCode #SoftwareArchitecture #ObjectOrientedDesign #CodingWithExamples #CodeBetter #8WeeksLLDChallenge #JSON