The work done T172905 resulted in the availability of the mw.wikibase.getBestStatements function that helps makes tracking Wikidata more efficient. At rowiki, this has helped us drastically reduce the tracking of entire entities and made queries more efficient.

We could still do more; especially if we had some function that doesn't limit itself to just the "best" statements for an entity. We have some use cases that might benefit from that.

One example is our HistoricalCountries module which lists all the countries in which a city (or anything for that matter) was throughout history. In this case, P17 (country) for the entity will have one 'preferred' statement (with the current country), as well as more 'normal' statements, with P580 and P582 qualifiers for the historic ones. We also do a lot more magic with these 'normal' statements hidden beneath one or more 'preferred' ones: we extract the country and official name of a town for a specific date in time - for instance, to show that when Max Born was born (pun not intended) in 1882, he was born in Breslau, German Empire, not Wrocław, Poland (as it is today). We do similar stuff with flags for countries that changed their flag throughout their existence.

So, we still have a lot of code that loads an entire entity just to cycle through the claims associated with only one property, and the usage tracking of these entities could be helped a lot by something similar to mw.wikibase.getBestStatements, only with the 'best' part left out.