I hope my question is suitable for this site and is not too broad but I am having trouble designing the following architecture:
I have two sites. Site 1 is responsible for transferring credits between users. Site 2 is responsible for providing these users with services/products which can be paid with the credits they own in Site 1.
Lets say I have 1000 credits on Site 1. I have a service/product which costs 50 credits on Site 2 and a user wants to purchase it with his amount of credits he owns in Site 1.
Both sites communicate with REST. So for example when a user wants to purchase a service/product Site 2 prepares its request and sends it to Site 1 which makes the transaction and confirms to Site 2 that the transaction was successful (e.g. the user had enough credits for the service/product and those credits were successfully transferred to the destination)
Now here's the tricky part. In Site 1 I have the following logic:
Begin transaction
update user set credits -= 50 where id = 1
update user set credits += 50 where id = 2
REST CALL (Site 2) Success
Site 2 response - OK, commit transaction
Commit
Since REST is a call to a different site the transaction might take some time to complete. In the mean time is the whole table locked for any transactions or are the rows for user 1 and user 2 locked? Is this the proper way to implement my logic? Am I missing something?
Thank you in advance.