Which performance metric is typically considered best for web-performance optimization in traditional web applications?

User action duration is often regarded as a key performance metric for web-performance optimization in traditional web applications because it directly correlates with user experience. This metric measures the total time taken for user actions, such as clicking a button or loading a report, providing a holistic view of how quickly users can interact with the application. By focusing on user action duration, teams can identify bottlenecks that might affect user interactions, ensuring a more responsive and engaging application.

In contrast, while page load time measures the time it takes for a webpage to fully load for a user, it does not necessarily reflect the performance of user interactions after the page has been loaded. Similarly, speed index focuses on how quickly content is visually populated on the page, which is important but does not capture overall user interaction. Visually complete indicates when the full visual content has loaded, but like page load time, it does not take into account how quickly users can interact with the displayed content. Thus, the emphasis on user action duration provides a deeper insight into the actual experience users have while using the application.