A comprehensive subscription management system with integrated payment processing, multi-tier user hierarchies, and automated billing workflows for a European SaaS business model.
Project scope
Solo full-stack development of payment and subscription infrastructure. Built over 12+ months with continuous feature expansion and payment provider optimization.
Responsibilities
- Implemented multi-provider payment architecture supporting Mollie and PayPal with seamless provider switching and fallback mechanisms
- Integrated ActiveCampaign API for automated contact synchronization, custom fields management, and email marketing workflows
- Created robust subscription lifecycle management including upgrades, downgrades, recurring billing, payment grace periods, and failed payment recovery
- Developed payment provider abstraction layer with support for multiple payment methods (credit card, SEPA) and custom validation strategies
- Built automated invoice generation system with tax calculations, credit notes, and PDF generation for compliance requirements
- Implemented event-driven architecture for payment callbacks, subscription state changes, and commission calculations
- Created CLI commands for subscription plan synchronization across payment providers and background payment verification
- Designed email notification system for payment failures, subscription renewals, and customer communications
- Optimized payment processing workflows with queued jobs for transaction fetching and invoice generation
Outcomes & results
The payment infrastructure processes 1000+ recurring subscriptions with automated billing cycles, reducing manual invoice generation by 95%. Implemented payment provider abstraction layer eliminated vendor lock-in, enabling seamless migration between Mollie and PayPal. Automated subscription state management and grace-period handling reduced failed payment churn by handling transient failures gracefully.
Key accomplishments
- Integrated 2 major payment gateways (Mollie, PayPal) with 3+ payment methods (credit card, SEPA, PayPal wallet)
- Built API abstraction handling 5+ payment provider endpoints per provider (~20 total API integration points)
- Designed subscription state machine supporting 8+ subscription states (active, pending, failed, grace period, cancelled, expired, etc.)
- Created automated invoice generation producing 100+ invoices monthly with tax calculations and compliance requirements
- Implemented payment callback handling with comprehensive logging supporting audit trails and debugging
- Reduced payment processing manual work from 2 hours daily to <15 minutes via automation
Skills gained
- Multi-provider payment gateway integration and PCI compliance
- Subscription-based billing systems and revenue recognition
- Event-driven architecture and webhook handling
- Third-party API integration and data synchronization
- GDPR-compliant user data management
- Background job processing and queue management