# Coupon Distribution System
0) Problem Restatement
Design a highly scalable system that can generate and distribute unique, trackable coupons to millions of users. The solution must support personalization, real-time redemption validation, lifecycle tracking, and seamless integration with a CRM for targeted campaigns and analytics.
1) Requirements
1.1 Functional
- Generate coupons: Unique codes per user, tied to specific campaigns.
- Track metadata: Expiry, discount type/value, usage limits.
- Support types: One-time and multi-use coupons.
- Real-time validation: Validate and apply coupons at checkout in under 100ms.
- CRM Integration: Targeted audience segmentation and campaign triggers.
- Event tracking: Emit events for issued, delivered, redeemed, and expired coupons.
1.2 Non-Functional
- High Scalability: Support millions of users and thousands of redemptions per second.
- High Availability: ≥ 99.9% uptime.
- Security: Prevent tampering, brute-force, and replay attacks.
- Auditability: Complete audit trails for ROI and fraud detection.
1.3 Scale Estimates
- Users: 100 million.
- Campaigns: 10,000 active campaigns.
- Redemptions: 5,000 requests/sec peak.
- Storage: Highly compressed coupon records for historical tracking (billions of rows).
1.4 API Design
The core APIs required for the service:
- Get Coupons:
GET /v1/coupons- Fetch active coupons for a user. - Generate Coupon:
POST /v1/campaigns/:id/issue- Issue a new coupon for a user. - Redeem Coupon:
POST /v1/coupons/redeem- Validate and apply a coupon. - Track Event:
POST /v1/events- Log coupon usage events.
2) High-Level Architecture
2.1 Overview
- Campaign Engine: Orchestrates user selection and issuance rules.
- Coupon Generator: Creates unique codes and persists metadata.
- Redemption API: Validates and tracks coupon state in real-time.
- Analytics: Aggregates usage events for ROI and fraud detection.
2.2 Architecture Diagram
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