Nginx load balancing scenario with 2 locations
We're planning to create an environment with load balancer(s) and app servers (running php apps). We have servers currently on Amsterdam and Helsinki. So my question is that is it ok to create load balancer which transfers traffic to both Amsterdam and Helsinki (on least connections rule) or should the all servers exists on same location? Or could some geolocation module on Nginx be advisable? Also if these app servers are using MongoDb and/or MariaDb, where should db server(s) go?