A Serverless Event-Driven Framework for Scalable Subscription Billing Using Function-as-a-Service and Automated Build Pipelines

Abstract: The proliferation of subscription-based commerce has intensified the demand for billing systems that can process recurring charges, prorations, and usage-based fees reliably at fluctuating scale. Traditional billing platforms are typically deployed on continuously provisioned servers, which incur idle cost during quiescent periods, scale coarsely under sudden demand, and entangle billing logic with infrastructure management. This study proposes a serverless, event- driven framework that administers the complete subscription billing cycle through stateless functions invoked on demand. The methodology decomposes billing concerns—subscription management, invoice generation, payment processing, usage metering, and notification—into independent functions exposed through a managed application programming interface gateway and coordinated by event and schedule triggers. Business logic is implemented in Python, while a Node.js client layer mediates user interaction, and an automated build service compiles, tests, packages, and deploys function revisions without manual provisioning. An experimental evaluation conducted across concurrency levels from fifty to thirty-two hundred simultaneous requests demonstrates that the serverless framework sustains an average latency of approximately 140 milliseconds at moderate load and degrades only gradually under heavy concurrency, whereas a provisioned-server baseline exhibits steep latency growth beyond four hundred concurrent requests. The framework attains a scaling efficiency near 94 percent and reduces cost per million requests by more than fourfold relative to the baseline, at the expense of occasional cold-start latency. The principal contributions comprise an event-driven billing architecture, a pipeline-automated deployment model for functions, and an empirical cost-performance analysis validating function-as-a-service for elastic billing workloads.

Keywords: Serverless computing, function-as-a-service, subscription billing, event-driven architecture, API gateway, continuous deployment, scalability, cloud cost optimization.