A frontend take on Jeff Dean's "Latency Numbers Every Programmer Should Know". Web page load times and responsiveness to user action in web apps is a primary driver of user satisfaction–and both are often dominated by network latency. Latency itself is a function of the user's connection to the internet (Wifi, LTE, 5G), how far away the server is that the user is connecting to, and the quality of the network in between. While the latency numbers may seem low by themselves, they compound quickly. For example, a network waterfall of depth 3 on a 300ms link leads to a total latency of 900ms. Technologies like React Server Components can move network waterfalls to the server where the same request pattern might be 100 times as fast. Metric Estimate Metric Impact Wifi latency to internet Wifi adds minimal latency to a connection. This can increase with a weak signal or older hardware. 1-4ms TTFB, FCP, LCP 5G high-band (millimeter wave) latency to internet Millimeter wave is the fastest deployed mobile technology.…