Like we cache whole entities in Lua, we should also cache individual statements loaded via php.getEntityStatements, this is especially important as serializing Statements for Lua is fairly expensive.
|mediawiki/extensions/Wikibase : master||Track mw.wikibase in memory statement cache misses|
|mediawiki/extensions/Wikibase : master||In Lua cache mw.wikibase.getBestStatements/getAllStatements|
|mediawiki/extensions/Wikibase : master||Generalize internal cache in mw.wikibase.lua|
Yes, I think so. According to the new "Wikibase lua getEntityStatements cache (daily average) " panel on the wikidata-lua-function-usage dashboard, we achieve more than decent hit rates for both Wikipedia and many sister projects, and exceptional hit rates for commons (way more hits than cache misses).