Common Performance Issues

One common issue encountered is the use of single page apps (SPA) which does not play nicely with core web vitals. This can result in slower performance due to data loss, leading to a poor user experience. Another issue is the use of microservices and micro front-ends, which can introduce latency due to multiple API calls. Additionally, the practice of using API subdomains can lead to preflight requests and added latency. Progressive JPEGs are also highlighted as a potential performance concern, as they may not always provide meaningful content on the screen faster. Overall, common problems include designing for the largest bit of content rather than the most important, misunderstanding the impact of certain design choices on performance, and failure to prioritize the end-user experience over performance metrics.