Evaluating Frontend Scalability Bottlenecks in Cloud-Backed High-Traffic Web Applications

Abstract

In high-traffic web applications powered by cloud backends, frontend performance is often the critical determinant of user experience (UX), retention, and conversion. While backend scalability is typically addressed through horizontal scaling and microservices, client-side bottlenecks—stemming from excessive JavaScript bundle sizes, inefficient asset loading, and slow hydration processes—frequently emerge as the new, non-linear constraints on application scalability. This study proposes a Holistic Frontend Scalability Assessment Model (HFSAM) that systematically evaluates the performance ceiling imposed by client-side factors under simulated high-traffic conditions. HFSAM employs a combined analysis of Core Web Vitals (CWV) metrics and server resource utilization metrics during peak load simulations. The empirical evaluation reveals that a $\mathbf{30\%}$ reduction in the main JavaScript bundle size translated to a $45\%$ improvement in Time-to-Interactive (TTI) for low-end mobile devices and a $15\%$ reduction in peak server CPU load due to decreased API dependency fetching during the hydration phase. This confirms that optimizing the client-side execution budget is essential not only for UX but also for improving the overall resource efficiency and scalability ceiling of the entire cloud-backed system.