Power analysis is the process of estimating how many users you will need in order to detect an effect of a given size, or how small an effect you can detect.
For ecommerce and subscription apps, track purchase value, count, frequency, and rate.
Use page view counts and rates in conjunction with other metrics to construct ratios and funnels.
Page Load Performance
Use on-page events such as page load timing and load failures to understand performance.
Progressive delivery uses feature flags to increase speed and decrease deployment risk, and uses a gradual process for rollout and ownership.