Design
Coupon & Discount System
Design a flexible coupon and discount management system for an e-commerce platform supporting various promotion types.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
Discount rules multiply fast in the real world — this question checks whether your design lets new coupon types be added without rewriting the checkout logic each time.
02 - Where this system exists in the real world
You interact with this design every day.
E-commerce coupon and promo-code systems
Loyalty program discount engines
Subscription billing discount management
03 - What you'll master
Solve this once. Know it forever.
Model multiple discount types uniformly
Validate eligibility and stacking rules
Track usage limits per coupon/user
04 - What you'll design
7 functional · 3 non-functional requirements.
Create coupon codes with type: percentage off, flat amount off, free shipping, buy-X-get-Y
6 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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