Deadline was 2-3 days for product launch and doing distributed transactions was not an opinion as it requires heavy modifications.

I was doing money transfer app between one transactional system and one not transactional system so the way I did it was :
1. transfer money from one system to my app that was using Akka STM ( software transactional memory)
2. try to transfer money to second system
3. transfer money back on failure

There was no database, no state only transactional log as installing database would require to much time and paper work.

Sometimes transfer back failed so we need to look back at logs and search for money, it was quite easy cause there was error and there were not so many failed transactions like this.
About one or two in a month and everyone accepted that.

I started to write some sort of reconciliation thread but then was assigned to other work and it worked like this for couple of years transferring couple millions worth of transactions.