Yes, I agree with this. In SWI-Prolog, in addition to library(persistency), there are already some published results on transaction support for the internal dat

Yes, I agree with this. In SWI-Prolog, in addition to library(persistency), there are already some published results on transaction support for the internal database, which will give you some features that facilitate such use cases. This is already available and in fact also running for production web apps, but currently only for the RDF database. It is true that if you need more advanced functionality that dedicated database systems readily give you, then you have to wait until such features become available in SWI-Prolog, pay for their implementation, or resort to using an external database for which there often are bindings.