Historically the de-facto standard Ruby gem for multi-tenancy in Rails, providing schema-per-tenant and database-per-tenant switching. For the database-per-tenant case, it re-establishes Active Record connections on switch — a pattern that is not thread-safe and can silently corrupt data on threaded servers like Puma, while being masked on fork servers like Unicorn. The original authors publicly stated the schema-level approach did not work for them in the long run.