What would you suggest instead of mongodb for large scale production db? Our DB size is growing on daily basis and currently near to 200GB on a dedicated machine.
It depends -- if it's analytics, I'd look to ship it to a hosted system (I like BigQuery). If it's not, you might be able to scale up to terabyte or two before sharding; then maybe cassandra or one of the sharded postgres things (Citus, postgres-xl?)? I haven't had that problem in awhile.
Depends on data. If it's time series data then I would use time series database like InfluxDB. But again you might be fine even with Postgres or Mongo. Depends on structure and type of data.
Postgres or cassandra depending on scale and use case.