Community Blog What Is ApsaraDB PolarDB And Why Choose It

What Is ApsaraDB PolarDB And Why Choose It

This article will explain the reason that PolarDB is a next-generation relational database, in terms of its benefits, architecture, etc.

The Overview of PolarDB

Apsara PolarDB is no doubt a next-generation relational database that is developed by Alibaba Cloud. PolarDB includes 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 PolarDB cluster can support a maximum storage space of 100 TB. You can add a maximum of 16 nodes to each PolarDB cluster. PolarDB can be applied to several different scenarios.

PolarDB uses an architecture that allows you to decouple and separate computing and storage. In this case, all compute nodes share the same physical storage. PolarDB allows you to upgrade or downgrade instance specifications within minutes, and to perform fault recovery within seconds. ApsaraDB for PolarDB ensures global data consistency. It also provides data backup and disaster recovery services free of charge. PolarDB for MySQL has the benefits of both commercial databases and open-source cloud databases. Commercial databases are stable and scalable and have high performance. Open source cloud databases are easy to use and feature rapid iteration. For example, the performance of PolarDB for MySQL is six times that of MySQL. However, the cost of a PolarDB for MySQL database is only 10% that of a commercial database.

  • Computing and storage decoupling, shared distributed storage
    Apsara PolarDB decouples computing from storage. This meets your business requirements for auto-scaling. All 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, read/write splitting
    Apsara PolarDB Cluster Edition uses a distributed cluster architecture with multiple nodes. Each PolarDB cluster consists of one primary node (read/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 distributes read requests to read-only nodes for load balancing. The proxy allows applications to access PolarDB for MySQL by using the same method that is used to access a single-node database.

Apsara PolarDB Video

See how PolarDB can save you from tedious operations, exhausted troubles, and challenges coming from uncertainty.

The Benefits of PolarDB

PolarDB is ease of use

PolarDB is compatible with a variety of popular relational database engines. It is fully compatible with MySQL and PostgreSQL, and is highly compatible with Oracle syntax, with little or no code and application modification.

PolarDB is cost efficiency

  • Separation of computing and storage: Compute nodes share storage resources. You only pay for compute nodes when you add read-only nodes, which greatly reduces scale-out costs.
  • Serverless storage: You do not need to manually configure storage space, because the storage space is automatically scaled based on the data volume. You only need to pay for the database capacity that you have used.

PolarDB is with high performance

  • With an improved database kernel, Apsara PolarDB supports physical replication, RDMA protocol, and shared distributed storage, which greatly improves performance.
  • An Apsara PolarDB cluster contains one primary node and up to 15 read-only nodes. The cluster meets performance requirements in high concurrency scenarios, particularly suitable for scenarios where read requests are far more than write requests.
  • An Apsara PolarDB cluster shares storage among the primary node and read-only nodes. To apply data changes to nodes in the cluster, you only need to change data once.

PolarDB has storage capacity for hundreds of terabytes of data

Apsara PolarDB uses distributed block storage and a file system to allow automatic scale-up of database storage capacity, regardless of the storage capacity of each node. This enables your database to handle up to hundreds of terabytes of data.

PolarDB has high availability, reliability, and data security

  • Supports shared distributed storage to eliminate data inconsistency in the secondary database caused by asynchronous primary-secondary replication. This ensures zero data loss if a single point of failure occurs in a database cluster.
  • Supports a multi-zone architecture. Data replicas are available across multiple zones for database disaster recovery and backup.
  • Provides various security measures for your database access, storage, and management. These measures include setting an IP whitelist for database access, using VPC for network isolation, and creating multiple replicas for data storage.

PolarDB has rapid elastic scaling to handle workload spikes

  • Configuration upgraded or downgraded within 5 minutes
    Apsara PolarDB supports rapid CPU and memory expansion by using container virtualization and shared distributed block storage.
  • Nodes added or removed within 5 minutes
    Apsara PolarDB can dynamically add or remove nodes to help you improve performance and reduce costs. You can use cluster endpoints to mask changes at the underlying layer. In this case, applications are unaware of the addition or removal of nodes.

PolarDB is lock-free backup

Based on the snapshot technology of underlying distributed storage, Apsara PolarDB requires only a few minutes to back up a database with TB-level data. During the entire backup process, no lock is required, which delivers higher efficiency and minimizes the negative impact.

The Architecture of PolarDB

ApsaraDB PolarDB uses a cloud-native architecture. PolarDB takes advantage of the benefits of commercial databases and open-source cloud databases. Commercial databases offer the following benefits: stability, reliability, high performance, and scalability. Open source cloud databases offer the following benefits: simplicity, openness, and rapid iteration. This topic describes the architecture and features of PolarDB.


One primary node and multiple read-only nodes

PolarDB uses a distributed cluster-based architecture. Each standard PolarDB cluster consists of a primary node and a maximum of 15 read-only nodes. At least one read-only node must be used to implement failovers to ensure the high availability of PolarDB databases. The primary node processes read and write requests and the read-only nodes process only read requests. PolarDB uses an active-active architecture for the primary node and read-only nodes in each cluster. This architecture allows you to implement failovers to ensure the high availability of PolarDB databases.

Compute and storage decoupling

PolarDB decouples compute from storage. This allows you to scale clusters that are deployed on Alibaba Cloud to meet your business requirements. Compute nodes store only metadata and remote storage nodes store data files and redo logs. Database engine servers function as compute nodes and database storage servers function as storage nodes. You need only to synchronize the metadata of redo logs among your compute nodes. This reduces the replication delay between the primary node and read-only nodes. If the primary node fails, a read-only node can function as the primary node in a short period.

Read/write splitting

By default, read/write splitting is enabled for PolarDB clusters. The read/write splitting feature is available for free. This feature is transparent to users. This feature provides the capabilities of high availability and self-adaptive load balancing. The read/write splitting feature automatically forwards SQL requests to each node of PolarDB clusters based on cluster endpoints. This allows you to process a large number of concurrent SQL requests in high-throughput scenarios. For more information, see Read/write splitting.

High-speed network connections

High-speed network connections are used between compute nodes and storage nodes of PolarDB databases. The Remote Direct Memory Access (RDMA) protocol is used for data transmission between compute nodes and storage nodes. These two features eliminate the bottlenecks of I/O performance.

Shared distributed storage

In PolarDB, compute nodes share one set of data. This reduces your storage costs. PolarDB uses distributed storage and the distributed file system. This allows you to perform online scale-ups to increase the storage capacity of databases in a smooth manner. The online scale-ups are not affected by the storage capacity of each individual database server. The online scaling allows your databases to process hundreds of terabytes of data.

Multiple data replicas and the Parallel-Raft protocol

Storage nodes of PolarDB databases maintain multiple data replicas to ensure reliability and use the Parallel-Raft protocol to ensure data consistency among these replicas.

The Scenarios of ApsaraDB for PolarDB

ApsaraDB for PolarDB is widely adopted by users in New Retail, Gaming, Internet Finance, and Live-streaming.

PolarDB supports scenarios challenged by high concurrency and sudden traffic volume increase, such as in promotions and flash sales. Instances can be scaled out within seconds, meeting the read/write requirements for enterprise-level large-scale data analysis. Scale-out events can be quickly implemented and the availability of database clusters is enhanced while keeping storage costs at a minimum.


ApsaraDB for PolarDB is a cloud-native relational database compatible with MySQL, PostgreSQL, and Oracle. ApsaraDB for PolarDB provides the performance and availability of traditional enterprise databases and the flexibility and cost-effectiveness of open-source databases.

Related PolarDB Product:

ApsaraDB for PolarDB

ApsaraDB for PolarDB is designed for business-critical database applications that require fast performance, high concurrency, and automatic scaling. You can scale up to millions of queries per second and 100 TB per database cluster with 15 low latency read replicas. ApsaraDB for PolarDB is six times faster than standard MySQL databases and delivers the security, reliability, and availability of traditional commercial databases at 1/10 the cost. ApsaraDB for PolarDB embodies the proven database technology and best practices honed over the last decade that supported hyper-scale events such as the Alibaba Double 11 Global Shopping Festival.

On November 11, 2018, ApsaraDB for PolarDB successfully supported 1 billion orders in 24 hours, during which the number of queries received per second spiked by 122 times.

Related PolarDB Documentation

PolarDB for MySQL

100% compatible with open-source MySQL and RDS MySQL.

PolarDB for PostgreSQL

Decouple of computing and storage, extreme auto-scaling, lower TCO.

PolarDB for Oracle

High compatible with Oracle syntax, supports migration from all Oracle versions.

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