Rails protects production database

Rails has a mechanism to protect production databases to be dropped (and other destructive commands). In order to do that rails database tasks use a private database rake task check_protected_environments. Here's a db task code sample from rails code databases.rake:

task drop: [:load_config, :check_protected_environments] do
  db_namespace["drop:_unsafe"].invoke
end

Under the hood it checks the database environment from a metadata table ar_internal_metadata created by rails on the first load schema attempt

SELECT * FROM ar_internal_metadata;
     key     |  value 
-------------+---------
 environment | staging