This sounds similar to what I saw at a client a few years back. All XML responses from a REST API were inserted into a single VARCHAR(MAX) column (one row per response, but a response could have multiple "records") in a SQL Server database.

All interaction with this was through a byzantine web of XPath expressions using the severely neutered dialect of XQuery that shipped with SQL Server 2008.

Apologies for the mini-rant, your comment appears to have triggered some painful memories.

It's databases all the way down...