When several instances are connected to remote DB, then all their locks are managed in the IRIS instance where this DB

That's only partially true: they are kept in both LOCKTABs, on data server and on app server as well.
This behavior can be easily checked in Management Portal. So if one of app servers makes great trouble with LOCKs, it can affect other servers.

Muhammad, thank you for the good intro to container data persistense topic.

I'm a bit curious why ISC recommends 

--mount type=bind

in contrast to dockers recommendation

--mount type=volume

?

That's really elegant!