Are questions regarding the internal workings and the architecture of a particular software product (e.g. Oracle database, SQL Server, etc) within the scope of the site?
Such questions would probably not be accepted.
For closed-source applications, the question would either be generally unanswerable because it would require someone to have actually worked on the product or it would become a resource request to find an article, blog post, conference talk, or something similar. The average member of the community would not be able to give an authoritative answer to these questions.
For open-source applications, I'd need to see the specific question you had in mind, but I'd think that some would tend toward being highly opinionated or speculation. We may not know why one architectural decision was made, and if there is information that is available to the public, it would also tend to being a resource request question. There may be a small slice of such questions that would fit, though, so I can't give a blanket answer here.