What are the limitations of context filters?

The temporary table has to be built, and it is rebuilt every time the context filter changes. That is real work, so a context filter on a fast-changing quick filter can make a dashboard slower rather than faster.

Context is also a blunt instrument: it applies to the whole sheet, not to a single calculation, so you cannot scope it selectively.

The old advice that context filters improve performance came from a time when they materialised a smaller table for expensive queries. On modern versions with an extract, that benefit rarely appears.

Use them when you need the ordering — top N within a subset, or making a FIXED expression respect a filter — rather than as a general optimisation.