Yates is an extremely simple persistence engine - what you want to 'persist' you can send to Yates with 'YPTransactionLog add: #foo', and it is written to a transaction log that belongs to the image. The transaction log is a ReferenceStream, which can be trivially read back when a crash happens.
The goal of Yates is primarily simplicity - there's no model of when to log entries, or a transaction concept. Everything you send to it is written out, and on recovery everything that was written (and has not been obsoleted by a newer image snapshot) is read back.