Andrei Kaleshka's first English talk at wroclove.rb 2024 on preventing paid-account credential sharing in a Ruby on Rails music-education app. He walks through data collection with paper_trail and a login_sessions table, charting indicators in Metabase, rolling out devise-two-factor email MFA selectively to users with 4+ active sessions, and reports a ~27% lift in signups.
claude-opus-4-71e927be1