Before you use ApsaraDB for MongoDB, you must understand the limits of the instance architectures of Apsara for MongoDB, which helps you select the instance architectures that best suit your business scenarios.

Standalone instances

Feature Limit
Instance deployment Standalone instances can be created only in the following regions for single-zone deployment. You can also change the configurations of standalone instances. For more information, see Change the configurations of a standalone instance.
  • China (Hangzhou): Hangzhou Zone G, H, I, or J
  • China (Shanghai): Shanghai Zone B, D, or G
  • China (Qingdao): Qingdao Zone B or C
  • China (Beijing): Beijing Zone E, F, or H
  • China (Shenzhen): Shenzhen Zone E
  • Singapore (Singapore): Singapore Zone A, B, or C
Database version Standalone instances are supported only for MongoDB 4.0 and MongoDB 3.4.
Database connection Encryption features cannot be enabled or disabled for internal network access.
Data backup Only Snapshot Backup is supported.
Note A snapshot is a point-in-time backup of disk data.
Data restoration
Service availability High availability features including primary/secondary switchover, role switching, or instance migration across zones are not supported.
Data security
Log management Log management features including Slow Query Logs, Error Logs, or Running Logs are not supported.
CloudDBA Performance, Real-time Performance, and Sessions are supported. Storage Analysis or Slow Query Logs is not supported.
Data migration and synchronization

Replica set instances

Feature Limit
Instance deployment Replica set instances that run MongoDB 4.4 or 5.0 can be created only in the following regions for single-zone deployment:
  • China (Hangzhou): Hangzhou Zone G, H, or I
  • China (Shanghai): Shanghai Zone B or G
  • China (Qingdao): Qingdao Zone C
  • China (Beijing): Beijing Zone F or H
  • China (Zhangjiakou): Zhangjiakou Zone A or C
  • China (Hohhot): Hohhot Zone B
  • China (Shenzhen): Shenzhen Zone E
  • China (Heyuan): Heyuan Zone A or B
  • China (Chengdu): Chengdu Zone A or B
  • Singapore (Singapore): Singapore Zone A, B, or C
  • US (Silicon Valley): Silicon Valley Zone B
  • US (Virginia): Virginia Zone A or B
Database version MongoDB versions and storage engines of replica set instances impose constraints on each other. For more information, see MongoDB versions and storage engines.
Replica set instance creation
  • A replica set instance automatically created by ApsaraDB for MongoDB consists of a primary node, a hidden node that is invisible to users, and one or more secondary nodes.
  • You can change the configurations of a replica set instance when the instance is running. For more information, see Change the configurations of a replica set instance.
    Note
Minor database version To ensure better performance and stability of the instance, the system will upgrade the minor version to the latest version by default. If the minor version of your instance expires or is not included in the maintenance list and the instance is upgraded, migrated, changed, Created from a backup, Created by point-in-time, or performed Restore one or more databases of an ApsaraDB for MongoDB instance.
Database connection You cannot migrate replica set instances that run MongoDB 4.4 from the classic network to a VPC.
Data backup
  • Physical Backup and Logical Backup are supported for replica set instances that run MongoDB 4.2 or earlier.
    Note If the database version of a replica set instance is MongoDB 3.2 or 3.4, the total number of collections and indexes in the instance cannot exceed 10,000. Otherwise, physical backup may fail. If your business involves more than 10,000 collections and indexes, you can create a replica set instance that runs MongoDB 4.0 or 4.2 or upgrade the database version of the instance to MongoDB 4.0 or 4.2. For more information about how to upgrade the database version, see Upgrade MongoDB versions.
  • Snapshot Backup is supported for replica set instances that run MongoDB 4.4.
    Note A snapshot is a point-in-time backup of disk data.
Data restoration Data restoration is supported only for three-node replica set instances. For more information, see Restore backup data to the current instance.
Data security
Note Audit Logs or TDE is not supported for replica set instances that run MongoDB 4.4.
Log management Log management features including Slow Query Logs, Error Logs, or Running Logs are not supported for replica set instances that run MongoDB 4.4.
CloudDBA The Slow Query Logs feature is not supported for replica set instances that run MongoDB 4.4.
Data migration and synchronization

Sharded cluster instances

Feature Limit
Database version MongoDB versions and storage engines of sharded cluster instances impose constraints on each other. For more information, see MongoDB versions and storage engines.
Sharded cluster instance creation
  • When you create a sharded cluster instance, you can specify the specifications and numbers of mongos and shard nodes.
  • You can also add or remove mongos or shard nodes to or from a sharded cluster instance when the instance is running. For more information, see Overview.
    Note
    • A mongos node can be released for a sharded cluster instance that has at least three mongos nodes. However, at least two mongos nodes must be retained for a sharded cluster instance.
    • A shard node can be released for a sharded cluster instance that has at least three shard nodes. However, at least two shard nodes must be retained for a sharded cluster instance.
    • Before you release a shard node from a sharded cluster instance, make sure that the data of the shard node can be offloaded onto the remaining shard nodes in the sharded cluster instance. Otherwise, the sharded cluster instance stays in the Deleting Node state. In this case, you cannot perform operations such as resetting the password, switching roles, modifying the node connection string, and modifying parameters.
Minor database version To ensure better performance and stability of the instance, the system will upgrade the minor version to the latest version by default. If the minor version of your instance expires or is not included in the maintenance list and the instance is upgraded, migrated, changed, Created from a backup, Created by point-in-time, or performed Restore one or more databases of an ApsaraDB for MongoDB instance.
Data read and write You can only read data from the admin database of a sharded cluster instance, and you cannot write data to the admin database.
Data backup Physical Backup and Logical Backup are supported for sharded cluster instances.
Data restoration Only point-in-time data restoration is supported. For more information, see Restore backup data to a new ApsaraDB for MongoDB instance by point in time.
Data security
Note Only the VPC network type is supported for DynamoDB-compatible sharded cluster instances. For more information about how to create a VPC, see Create and manage a VPC.
CloudDBA CloudDBA is not supported for DynamoDB-compatible sharded cluster instances. CloudDBA features include Performance, Real-time Performance, Sessions, Storage Analysis, and Slow Query Logs.
Data migration and synchronization
Recycle The Recycle feature is not supported for sharded cluster instances.