Multi-tenant Back-end Architecture for IoT-based Postpaid Smart Water Meter Monitoring and Billing Systems

Abstract

Smart Water Meter (SWM) systems based on the Internet of Things (IoT) enable automatic and real-time water consumption monitoring. However, multi-tenant residential environments require a back-end architecture capable of integrating IoT telemetry ingestion, tenant data management, postpaid billing, and payment synchronization within a unified platform. This study proposes a modular back-end architecture that combines IoT telemetry ingestion, logical multi-tenant data isolation, and asynchronous postpaid payment synchronization. The proposed architecture is implemented using Node.js, Express.js, PostgreSQL, and Prisma ORM, with webhook-based payment synchronization. The system was developed using Prototyping methodology and evaluated through functional, payment synchronization, and performance testing under concurrent workloads. The results demonstrate that all functional requirements were satisfied and payment transactions were successfully synchronized with the centralized database through the webhook mechanism. Performance evaluation across 100, 200, and 300 concurrent virtual users shows that the architecture maintains stable response times under moderate load, with the dashboard endpoint consistently achieving the lowest response time, while P95 latency increases from 365.85 ms at 100 virtual users to 1,815.91 ms at 300 virtual users, reflecting the impact of rising concurrency on the application and database layers. These findings indicate that the proposed architecture provides a scalable back-end solution for multi-tenant Smart Water Meter systems, offering reliable telemetry processing, postpaid billing management, and payment synchronization while also revealing the concurrency thresholds that inform future scalability improvements.