Suppose we have a service, which holds user balance in Bitcoin.
How to implement withdrawal from bitcoin perspective?
Which RPC call to use? How to archive transaction to have a proof of sending money to user? How to prevent duplicate money send in corellation to SQL transaction?
The most important thing is to prevent dual-submission having in mind power loss at any time. So we should have a way to mark some money as "possible sended" + some way to check in future time if it really was succesfuly sended and stored in blockchain.
(note that I am not asking about security, ACID transaction itd. I am interested in a way to comunicate with wallet daemon service)