PolarDB for Xscale (PolarDB-X) is a cloud-native distributed database built by Alibaba Cloud. It scales horizontally without sharding configuration, survives node and data center failures with zero Recovery Point Objective (RPO) and Recovery Time Objective (RTO) under 10 seconds, and runs hybrid transactional and analytical (HTAP) workloads on a single data source—all while staying fully compatible with MySQL.
Architecture
PolarDB-X starts as a centralized MySQL-compatible database and scales into a distributed system as your workload grows, without requiring database changes or application migrations.
Internally, PolarDB-X separates storage from compute using an x86-based shared-nothing architecture. Each layer scales independently based on your workload demands.
Features
PolarDB-X is fully compatible with the MySQL open-source ecosystem—including SQL syntax, transaction behaviors, and ecosystem tools. Migrating from a self-managed MySQL database requires minimal code changes.
| Feature | Description |
|---|---|
| Financial-grade high availability (RPO=0) | Zero RPO and RTO under 10 seconds, backed by a self-developed Paxos algorithm. Every write requires majority-node confirmation, so the cluster keeps serving traffic even when a node fails. Three deployment configurations are available: three replicas in a single data center, three replicas across three data centers in one region, or five replicas across three data centers in two regions. |
| Transparent distribution | Distribute data without configuring sharding. PolarDB-X shards on the primary key by default, so you can migrate existing data without specifying a partition key. During scale-out, PolarDB-X uses consistent hashing for partitioning and rebalances data across nodes with no downtime; it can offload requests from overburdened nodes to mitigate hotspots and achieve load balancing. PolarDB-X also supports parallel queries and throttling to ensure business continuity during scaling. The self-developed X-Paxos protocol maintains zero RPO during failovers, while Timestamp Oracle (TSO) and distributed Multi-Version Concurrency Control (MVCC) enforce isolation and consistency across all distributed transactions. PolarDB-X also provides binary logging to resolve data-forwarding issues in distributed databases: it ensures data consistency before backup and creates backup files based on globally consistent data, preventing inconsistency when nodes are restored from backup files created at different points in time. |
| Integration of centralized and distributed architectures | Start with Standard Edition (100% native MySQL compatible) and upgrade to Enterprise Edition without service interruption when your workload outgrows a single node. Enterprise Edition is highly compatible with native MySQL. After the upgrade, distributed components automatically connect to existing data nodes—no data migration, no application changes. |
| HTAP | Run transactional and analytical queries on the same data source. PolarDB-X combines row store nodes with column store nodes, a clustered columnar index (CCI), cost-based optimizers, and vectorized operators to serve both workload types. Cold data archiving (TTL) and a self-developed SQL engine complete the HTAP experience. |
| Open-source ecosystem and multi-cloud deployment | Deploy where your compliance and infrastructure requirements dictate. Choose from four options based on your environment: Alibaba Cloud public cloud (fully managed, 13 regions worldwide) for fast iteration and managed operations; Apsara Stack for regulated or isolated environments with compliance requirements; DBStack for on-premises high-performance deployments; or PolarDB-X Lite for lightweight distributed clusters with minimal resource usage. |
| Security and stability | PolarDB-X has passed several national-level security certifications and is deployed in the core systems of finance and telecommunications companies. Available security controls include IP address whitelists, SSL, transparent data encryption (TDE), backup encryption, always-confidential computing, SQL audit and tracing, full SQL Auditthree-role mode, and tag permissions. For disaster recovery, PolarDB-X meets the level 5 standards of the finance industry and supports deployment across three data centers in two regions. |
Use cases
| Use case | What PolarDB-X provides |
|---|---|
| High-throughput transactional systems | Financial and internet transaction systems need long-running, low-latency, strongly consistent operations. Financial-grade high availability and transparent distribution keep transaction systems consistent and available under heavy load. |
| Centralized data storage (ODS) | Aggregating business data from multiple vertically split sources into an operational data store (ODS) requires high-write concurrency, large-scale storage, and multidimensional queries. Transparent distribution, HTAP, and built-in security controls handle these demands without adding operational complexity. |
| Database and table sharding | Workloads requiring high throughput, high concurrency, and distributed DDL operations (including scaling) map directly to PolarDB-X's transparent distribution capability, which manages sharding automatically. |
| Migration from single-node to distributed architecture | When a single-node database can no longer handle the workload—or when a single table grows too large to maintain—PolarDB-X lets you upgrade from Standard Edition to Enterprise Edition without downtime or application changes. See integration of centralized and distributed architectures. |
| Modular disaster recovery | Finance and telecommunications workloads require data center-level fault isolation and active geo-redundancy. Financial-grade high availability, transparent distribution, and security certifications support the modular, distributed architecture needed for this level of resilience. |
| Real-time HTAP queries | Applications that need real-time analytics alongside transactional operations on the same data can use PolarDB-X's HTAP capability without data duplication or consistency trade-offs. |
| Cost optimization and MySQL migration | Workloads with stable traffic patterns benefit from PolarDB-X's one-click MySQL migration path, data compression, and the ability to start on a centralized architecture and scale only when needed. Integration of centralized and distributed architectures, HTAP, and open-source ecosystem support contribute to lower total cost of ownership. |
| Multi-cloud disaster recovery | PolarDB-X supports Alibaba Cloud public cloud, Apsara Stack, DBStack, and PolarDB-X Lite, giving you the flexibility to deploy across multiple environments and avoid vendor lock-in. |