A dashboard that recomputes every user's cumulative metric from the very first day of an experiment, every single time it refreshes, is doing strictly more work each day the experiment stays open — by the fourth week, a daily refresh is rescanning four weeks of history to add one day of new information. This chapter covers the alternative: a state table that only ever absorbs yesterday's increment.
The Problem With Recomputing From Scratch
Every chapter so far has queried straight from the raw event tables...