Explore performance optimization techniques for web applications in this PHP UK Conference talk. Learn how to enhance user experience through improvements at every layer of the stack, from backend to browser. Discover the impact of milliseconds on user engagement and revenue. Delve into topics such as EdgeSide Includes, image compression, perceptual quality, structural similarity for images, predictive browsing, DNS prefetch, link rel preconnect, prerender, preload headers, and HTTP/2 Server Push. Understand the importance of time in relation to money, ads, compression, prefetching, and HTTP/2 upgrades. Examine compression engines, browser support, security implications, and benchmarks for transitioning from HTTP to TLS.