We want to go to XtraDB cluster. Ver 5.7 Is there a white paper or assistance on determining if our Mysql Usage and transactions are compatible with XtraDB cluster? There is mention of long running transactions, how long is too long? how big is too big?
You should be upgrading to PXC 8.0 as this is the latest/current version. PXC8 includes the new Galera 4 which has ways of mitigating long running transactions if they become a problem. Let us know your general QPS and your read/write ratio%. There are not many situations where PXC is not a good fit for achieving high-availability with MySQL.