The idea is not to query things from the persistent store. Instead you would keep all the data in memory. The persistent store is just there in case your server goes down. In case of OO, there would be one big object graph which you then navigate using the functionality available in your programming language. For example take a list of things, pass it through the filter function to pick what you want.

My feeling is that in traditional business apps you don't have so much needs to these random searches over huge amount of data. It's more about taking hold of one piece of the graph and then navigating to related objects (dummy example: search for customer, then start looking at that customers orders).

I'm not familiar with Smalltalk, but I'm sure there was some ideas related to persistence other than just ORM and relational database (but could be those ideas have been proven as bad over the years). I just find it a bit strange that we have been building these things pretty much the same way for the last 20+ years. Meanwhile the hardware has changed much. Even with quite small corporate hw budget you are looking at half a terabyte of RAM and tens of cores in a single server.