Common Fallacies in Web Application Performance

In this article, José Valim addresses several common fallacies regarding web application performance. He emphasizes that performance should not be viewed as a production-only concern, as it significantly impacts development through aspects like compilation and application boot times. Valim explains that concurrency and effective use of multiple cores are essential for improving performance and that threads alone are not sufficient for multi-core concurrency. He also highlights the limitations of drawing conclusions solely from average response times and stresses the importance of considering high percentiles and user experiences during high load periods. Additionally, Valim points out that supposed cost-free solutions to performance issues often come with hidden costs, and the notion that the web is stateless is flawed given the reliance on databases and storage layers. Finally, he argues that while performance is crucial, it is not the only factor to consider when choosing technologies, noting that Elixir offers a balance of performance, developer productivity, and maintainability.