Views

A materialized view stores the result of a defining query so later reads can access those stored rows. It moves computation from every read into refresh operations, which can benefit repeated reporting queries. The tradeoff is an explicit freshness boundary and another relation to maintain; neither instant reads nor automatic synchronization with the source tables is guaranteed. ...

A view is a name for a query; a materialized view is that query’s result written down as data. You trade freshness for speed, and the trade only works if you decide how stale the readers can tolerate before you build it. ...