[yatsyk]

If I use backend I can create all validation logic in application server. But in this case no automatic synchronisation.

One of the major selling point of couchdb is replication protocol for client-server data syncing. When you design product with posgress you don't allow to execute raw sql queries from clients without any application server. But looks like it is recommended way to update data in couchdb world if you want to have synchronisation. I can't understand how can this architecture be secure?

[lhuser123]

Couchdb has options for controlling which documents are replicated. This may help depending on your use case.