Background. Modern web applications often rely on substantial client-side JavaScript, which can affect loading performance and perceived responsiveness under constrained network conditions. React Server Components (RSC) offer a hybrid rendering approach in which selected components are rendered on the server, potentially reducing client-side work. However, empirical evidence on how RSC affects both measured performance and user experience remains limited.

Objectives. This thesis investigated how a full-RSC implementation in a hybrid Next.js application compared with a CSR baseline under simulated 3G network conditions. The study focused on Largest Contentful Paint (LCP), client-side JavaScript transfer, and perceived user experience.

Methods. Two functionally similar e-commerce prototypes were implemented inNext.js: one without RSC and one with extensive use of RSC. Quantitative performance data were collected using repeated Google Lighthouse measurements under Chrome DevTools network throttling. A small exploratory within-subject user study with eight participants was conducted to examine perceived loading speed, responsiveness, and interaction smoothness.

Results. The full-RSC implementation produced mixed but partly favorable measured results. LCP improved clearly on the homepage, but worsened on the products page, while client-side JavaScript transfer was reduced modestly and consistently. The user study indicated that participants generally perceived the full-RSC versionas faster and smoother, even where quantitative gains were limited or mixed.

Conclusions. The results indicate that React Server Components can be useful under constrained network conditions, but their effect depends on page structure and implementation details. In this study, the main advantage of the full-RSC implementation was not consistent improvement across every metric, but a smoother user experience together with selected technical gains. The findings support evaluating rendering strategies with both performance measurements and user experience in mind.