Hybrid On-Premises and Cloud Infrastructure for Billing Software
Background
The client operated a legacy on-premises billing system handling sensitive customer data, meter readings, invoices, and payments. With growing data volume, remote work trends, and increasing regulatory demands, the company sought to modernize their billing infrastructure. However, fully migrating to the cloud posed risks around data residency, downtime, and control over critical systems.
Objectives
- Achieve scalability and improved uptime for customer-facing billing portals
- Retain control and security for sensitive data and mission-critical core systems
- Enable seamless data sync between cloud and on-prem systems
- Support future migration to full cloud, but with minimum disruption
Solution: Hybrid On-Premises & Cloud Architecture
Architecture Overview
- On-Premises:
- Existing billing database (Oracle/MySQL/SQL Server)
- Core computation engines and secure transaction processing
- LAN-based access for accounts & billing team
- Cloud (AWS/Azure/GCP):
- Customer self-service web portal (hosted as SaaS on cloud VMs/App Service)
- Mobile API endpoints (hosted in the cloud)
- Scalable reporting & analytics (using cloud data warehouse)
- DR (Disaster Recovery) backup with automated cloud snapshots
- Hybrid Integration:
- Secure VPN tunnel for real-time data sync (e.g., AWS Site-to-Site VPN, Azure ExpressRoute)
- Periodic ETL jobs to replicate data from on-prem to cloud warehouse
- Cloud application interacts with a proxy/microservice to request real-time billing info from on-prem
Deployment Flow
- User Access:
Customers and field staff access the billing portal via cloud-hosted web/mobile apps. - Data Flow:
- Read/write for bills, payments, and customer queries routed via secure API gateway.
- Sensitive transactions processed by on-prem system, results relayed to the cloud.
- Non-critical reports, analytics, and notifications handled entirely in cloud.
- Synchronization:
- Automated scripts replicate billing data to cloud data warehouse nightly.
- DR scripts backup on-prem billing DB to secure cloud storage (encrypted).
- Security:
- End-to-end encryption for all VPN and API traffic.
- RBAC for both cloud and on-prem environments.
- Regular audit trails on access and data movement.
Challenges & Solutions
| Challenge | Solution |
|---|---|
| Real-time data sync with low latency | Implemented a persistent VPN connection and lightweight event-based triggers for key billing events |
| Data residency and compliance | Core customer PII and billing info remained on-premises; cloud handled anonymized or less sensitive data |
| Downtime & DR | Automated backup and quick failover setup from on-prem to cloud using replicated storage snapshots |
| User experience for remote workers | Cloud-based portal ensured high availability and fast access; SSO integrated for secure logins |
Results
- 99.9% uptime for all customer-facing portals
- 50% reduction in reporting latency via cloud analytics
- Zero major security incidents post-migration (full compliance with local data residency laws)
- Future ready: Ability to gradually shift more workloads to cloud as business needs evolve
Conclusion
The hybrid on-prem/cloud architecture provided a best-of-both-worlds solution: secure, compliant, and resilient infrastructure for critical billing operations, while enabling scalability and a modern digital experience for customers.
This approach minimized business risk, allowed phased modernization, and created a strong foundation for future digital transformation.
