Materialized View
A precomputed, stored query result you read like a table — fast reads, at the cost of freshness.
A materialized view is the stored result of a query, physically saved so reads hit precomputed data instead of recomputing an expensive join or aggregation every time. Unlike a regular view (which runs its query on each access), it trades storage and freshness for read speed.
Worked example: a dashboard showing daily revenue over millions of orders can read a materialized view refreshed hourly in milliseconds, versus scanning the orders table on every load. Gotcha: the data is only as fresh as the last refresh — you choose between refreshing on a schedule (stale between refreshes) or incrementally on write (fresher but more overhead); a materialized view is a cache, with all a cache’s invalidation problems.