Funny you should use role/permissions as an example here, I spent the weekend using Claude Code to rewrite my own permissions engine to a new design that uses SQL queries to solve the problem "list all of the resources that this actor can perform this action on".

My previous design required looping through all known resources asking "can actor X action Y on this?". The new design gets to generate a very complex by thoroughly tested SQL query instead.

Applying that new design and updating the hundred of related tests would have taken me weeks. I got it done in two days.

Here's a diff that captures most of the work: https://github.com/simonw/datasette/compare/e951f7e81f038e43...