The engineering questions you get asked, and the bugs you actually hit. Drawn, one mechanism at a time, in the order the videos ship.
The page said welcome back, with somebody else's name on it. Four questions decide whether something in the path may answer instead of your server — and the default, when you say nothing at all, is not 'don't cache'.
A hundred sub-millisecond queries, a four-second page, and the two cuts the video could not afford: a batched second query is two points in time, and a thousand ids in an IN list is a problem of its own.
The planner never ignored it — it priced it. The two things the video could not say safely, then everything else it cut: index-only scans, partial and multicolumn indexes, trigrams, BRIN, statistics, HOT updates, bloat, and what LIMIT does to a plan.
