I will design it to cancel the subscription and ban the user’s account if the transaction does not appear in the blockchain 6 blocks later.
It's better if there is a system that waits for few hours before sending an email to the user that subscription maybe cancelled if transaction is not confirmed soon (1 confirmation). If the user fails to make the ...
60 API calls per minute
The Bittrex API employs call limits on all endpoints to ensure the efficiency and availability of the platform for all customers. In general, API users are permitted to make a maximum of 60 API calls per minute. Calls after the limit will fail, with the limit resetting at the start of the next minute.
Is the addmultisignature API call dependent on order of public keys in the array? Or is it lexicographically sorted?
Yes. It is not sorted according to BIP67 automatically.
How did I confirm?
I used the below command in bitcoin core:
addmultisigaddress 2 "[\"0318370919cfceb3d260081eeca3cae19f941eec321f597c48a64839178ea1e3e0\",\"...