PolarDBPolarDB is a relational database that is developed by Alibaba Cloud. PolarDB uses three independent engines. This ensures that PolarDB is fully compatible with MySQL and PostgreSQL. It also ensures that PolarDB databases are compatible with the Oracle syntax. Each cluster supports a maximum storage of 100 TB and contains up to 16 nodes. PolarDB is applicable to diverse scenarios for enterprises.


This topic describes ApsaraDB PolarDB PostgreSQL-compatible edition.

  • For more information about PolarDB for MySQL, see Overview.
  • For more information about PolarDB-O, see What is ?.

PolarDB uses an architecture that allows you to decouple and separate computing and storage. All compute nodes share the same physical storage. PolarDB allows you to upgrade or downgrade instance specifications within minutes, and perform failovers within seconds. PolarDB ensures global data consistency. PolarDB also provides data backup and disaster recovery services free of charge. PolarDB has the benefits of both commercial databases and open source cloud databases. Commercial databases are stable, scalable, and high-performance. Open source cloud databases are easy to use and feature rapid iteration

  • Computing and storage decoupling, shared distributed storage

    PolarDB decouples computing from storage. This meets your business requirements for auto-scaling. All compute nodes share the same underlying physical storage PolarStore by using the distributed file system PolarFileSystem. This significantly reduces your storage costs.

  • One primary node and multiple read-only nodes for read/write splitting

    PolarDB Cluster Edition uses a multi-node cluster architecture. Each PolarDB cluster consists of one primary node (read and write) and at least one read-only node. PolarDB uses PolarProxy to provide external services for the applications that are connected to cluster endpoints. The proxy forwards the requests from the applications to database nodes. You can use the proxy to implement authentication, data protection, and automatic read/write splitting. The proxy parses SQL statements, sends write requests to the primary node, and evenly distributes read requests to multiple read-only nodes. The proxy allows applications to access PolarDB for MySQL by using the same method that is used to access a single-node database.


You can use PolarDB in the same way you use MySQL, PostgreSQL, and Oracle. Compared with traditional databases, PolarDB has the following benefits:
  • Large storage capacity

    Each cluster provides a maximum storage capacity of 100 TB. You do not need to purchase instances for database sharding due to the storage limit of a single host. This simplifies the development of applications and reduces the workload of operations and maintenance (O&M).

  • Cost-effective
    • Shared storage: PolarDB decouples computing from storage. You are charged for only the computing resources when you add read-only nodes to a PolarDB cluster. However, you are charged for both computing and storage resources when you use traditional databases.
    • Elastic storage: You do not need to manually specify the storage capacity. The storage capacity is automatically scaled based on the data volume. You need to pay for only the storage that you use.
    • Storage plan: PolarDB provides subscription storage plans. To store a large volume of data, we recommend that you purchase subscription storage plans. Storage plans are more cost-effective than pay-as-you-go storage. You are offered higher discounts for storage plans with larger storage capacities.
  • High performance

    PolarDB significantly improves online transaction processing (OLTP) performance and supports more than 500,000 read requests per second and more than 150,000 write requests per second.

  • Elastic scaling within minutes

    PolarDB supports rapid scaling for computing. This is based on container virtualization, shared distributed storage, and the architecture that allows you to decouple and separate computing and storage. It requires only 5 minutes to add or remove nodes. The storage capability is automatically scaled. This does not interrupt your services.

  • Elastic scaling within minutes

    Log sequence numbers (LSNs) are applied to cluster endpoints. This ensures global consistency for read operations and avoids inconsistency that is caused by the replication delay between the primary node and read-only nodes.

  • Millisecond-level latency in physical replication

    PolarDB performs physical replication from the primary node to read-only nodes based on redo logs. The physical replication replaces the logical replication that is based on binary logs and improves the efficiency and stability of replication. No delay occurs even if you perform data definition language (DDL) operations on a large table, such as adding indexes or fields.

  • Accelerated backup within seconds

    It requires at most 30 seconds to perform full data backup for a large volume of data. During the backup, the database is not locked. This minimizes the impact of data backup on your applications. You can specify a time to back up the database data based on your business requirements.


For more information, see Specifications and pricing and Purchase a PolarDB cluster.

Usage notes of PolarDB

You can manage PolarDB clusters in the following ways. For example, you can create clusters, databases, and accounts.

  • Console: This provides a visualized web interface and simplifies management operations.
  • CLI: You can use the command-line interface (CLI) to perform all the operations that are available in the console.
  • SDK: You can use the SDK to perform all the operations that are available in the console.
  • API: You can call API operations to perform all the operations that are available in the console.

After a PolarDB cluster is created, you can connect to the PolarDB cluster in the following ways:

  • DMS: You can connect to a PolarDB cluster by using Data Management Service (DMS) and develop databases on the web interface of DMS. For more information, see Use DMS to connect to a PolarDB for MySQL cluster.
  • Client: You can connect to a PolarDB cluster by using common database clients, such as MySQL-Front and pgAdmin.


Before you purchase and use PolarDB, we recommend that you learn about the following terms:

  • Cluster: PolarDB Cluster Edition uses a cluster architecture. A cluster of consists of 1 primary node and a maximum of 15 read-only nodes.
  • Region: A region is a physical area where a data center is deployed. In most cases, PolarDB clusters are deployed in the same region as Elastic Compute Service (ECS) instances to ensure optimal access performance.
  • Zone: A zone is a physical area in a region. This area has an independent power supply and network. All zones in a region provide the same services.
  • Specification: A specification specifies the resources that are configured for each node, such as 2 CPU cores and 8 GB memory.

Related services

  • ECS: ECS instances serve as cloud servers. If your PolarDB clusters are deployed in the same region as the ECS instances and you access the PolarDB clusters through an internal network, the PolarDB clusters provide optimal performance. In most cases, ECS instances are used in combination with PolarDB clusters.
  • ApsaraDB for Redis: ApsaraDB for Redis is a database service that supports in-memory storage and persistent storage. You can use ECS instances, PolarDB clusters, and ApsaraDB for Redis instances to handle a large number of read requests and reduce the response time.
  • ApsaraDB for MongoDB: ApsaraDB for MongoDB provides stable, reliable, and scalable database services that comply with the MongoDB protocol. To meet various business requirements, you can store structured data in PolarDB and unstructured data in ApsaraDB for MongoDB.
  • DTS: You can use Data Transmission Service (DTS) to migrate on-premises databases to PolarDB clusters.
  • OSS: Object Storage Service (OSS) is a secure, cost-effective, and reliable cloud storage service that allows you to store a large volume of data.