Galera multi-nodes Master-Master issue with READ right after INSERT
This answer provided by @Bill Karwin explains how this is one of the drawbacks of Galera Cluster. 

What are the drawbacks of using Galera Cluster instead of Master/Slave Replication?

"...Therefore there's still a small chance of reading stale data from another cluster node. There's an option you can set to force SELECT to wait until the queue of worksets has updated the database, but this means you have delays on SELECT..."

Refer to this article on how to force the SELECT to wait for the most up to date data. http://galeracluster.com/2015/06/achieving-read-after-write-semantics-with-galera/ 

You will need to set the "wsrep_sync_wait" session variable.