Given your example:
https://github.com/corda/flow-db
I have a question.
Is it ok to create and store custom data within the Node database? Reading the Corda API Persistence section, I thought it could be used only to access the node database, and not to create new tables, etc. What would be a reasonable description of what can and what cannot be stored via CordaService?
It's totally OK to use Custom tables in Node. The ServiceHub actually provides you will a Connection Object. getServiceHub().jdbcSession(). As long as, you don't do some Update/Delete to the Nodes existing table you are fine. You can create any table you want and use it as per your need. As of now, corda doesn't expose JPA to map your tables to an Entity class. I guess you could see this feature in some future release.
