Actually I found one blog ('https://blog.bigchaindb.com/towards-a-public-bigchaindb-654619d93fac' ) here mentioned as it is public but in https://www.bigchaindb.com/features/ this link in features it's like 'bigchaindb can be a public or private'.
how to configure bigchaindb as a private blockchain?.
What is role based access control in bigchaindb.