You can migrate data from a user-created MongoDB database to an ApsaraDB for MongoDB instance. Please pay close attention to the limits of ApsaraDB for MongoDB.

Operation Limit
Deploy an instance Standalone instances can only be created in the China (Hangzhou), China (Shanghai), China (Qingdao), China (Beijing), and China (Shenzhen) regions.
Database version The MongoDB version must be 3.4.
Storage engine

The storage engine must be WiredTiger.

Public connection address Connecting to ApsaraDB for MongoDB instances over the Internet poses security risks. By default, only a VPC connection address is provided after an instance is activated. If you need to connect to an instance over the Internet, apply for a public endpoint. For more information, see Apply for a public endpoint.
Restart an instance You must log on to the ApsaraDB for MongoDB console or call the RestartDBInstance operation to restart an instance.
Migrate data For details about data migration, see Migrate user-created databases to Alibaba Cloud by using tools provided by MongoDB and Migrate user-created standalone MongoDB databases to Alibaba Cloud by using DTS.
Back up data Standalone instances are backed up in snapshot mode due to their special architecture.
Note Snapshot backups retain the state of disk data from a certain time point.
Restore data You can only create instances based on backup data. For more information, see Restore data to a new ApsaraDB for MongoDB instance by backup set.
Modify the parameters of an instance For security and stability purposes, some parameters cannot be modified. For more information, see Configure database parameters for an ApsaraDB for MongoDB instance.