Open Telekom Cloud for Business Customers

Distributed Database Middleware (DDM)

Distributed Database Middleware (DDM) is a database middleware service (to be developed into a distributed relational database service) that is compatible with MySQL licenses. It uses a storage-compute decoupled architecture that makes it easy to scale out compute and storage resources to handle a huge number of concurrent requests.

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Reasons for Distributed Database Middleware in Open Telekom Cloud

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Data import and export

External data can be imported to help you migrate databases to the cloud, and DDM instance data can be exported based on service requirements.

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Online monitoring

DDM monitors the read/write ratio and slow SQL logs on the console, helping you detect resource and performance bottlenecks as fast as possible.

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DDM console 

The DDM console enables you to manage and maintain DDM instances and schematics online.

Key Features of Distributed Database Middleware

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DDM is scalable in concurrency, computing, and data storage, freeing you from worrying about scalability and O&M issues as your services grow.

DDM is highly scalable, easy to use, quick to deploy, and cost-effective and can deliver high performance.

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Highly scalable

  • Provides automatic horizontal sharding
  • Allows you to change your instance class within minutes
  • Allows you to add instance nodes without impacting  applications
  • Allows you to add DB instances with minimal downtime.
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Easy to use

  • Compatible with MySQL licenses, syntax, and clients
  • Makes it easy to import data and migrate databases to the cloud
  • Splits read and write requests with no need to modify service code
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Quick to deploy

DDM instances are easy to deploy online. This shortens project cycles and helps migrate your services to the cloud. You do not need to purchase, deploy, or configure a DDM instance as you do for a self-built database.


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DDM provides stable performance, comprehensive O&M, and excellent technical support. With these advantages, it is more cost-effective than open-source products. Different instance classes are available, so there is always a choice well suited to your specific needs.

Architecture Use Case and Service

Grafik Architektur Use Case

Using a DDM instance is as if you are still using a single-node database no matter how many database shards there are. You can perform database O&M on the DDM console and connect to a database using the Java database connectivity (JDBC) driver or a MySQL client to read and write data, just as you would do with a single-node database.

Grafik Architektur Service


Supported functionalities



Horizontal sharding

When creating a distributed database, select a sharding key and DDM will generate a sharding rule to horizontally shard data by the sharding key.


DDM supports both compute and storage scaling. You can scale a DDM instance up or out  by adding nodes. Compute scaling is undetectable to your applications, and storage scaling minimizes service interruption to seconds.

Storage scaling can be implemented with two methods: rebalancing or resharding.

  • Rebalancing keeps the total database shards unchanged.
  • Resharding doubles the number of database shards.

Distributed transactions

DDM provides three types of transactions, including single-shard, FREE, and XA.

  • Single-shard: means that transactions cannot be committed across shards.
  • FREE: allows data to be written to multiple shards. If a transaction fails to be committed in some of the shards, the transaction is not rolled back which causes data inconsistencies.
  • XA: allows transactions to be committed in two phases. If a transaction fails to be committed in some of participating database shards, all work done will be rolled back to ensure data consistency.

SQL syntax

DDM is highly compatible with the MySQL licenses and syntax.

Read and write splitting

Read and write splitting is transparent to applications. You only need to create read replicas for a DB instance associated with your DDM instance and configure a read policy, without the need to modify application code. This function improves database performance and access efficiency, helping your applications process high-concurrency transactions.

Global sequence

DDM supports globally unique, distributed, and ascending SNs to meet requirements for primary or unique keys, or other specific requirements.


Available flavors




Memory (GB)











  • Currently, only MySQL DB instances of versions 5.7 and 8.0 are supported.
  • DDM does not support SSL for MySQL DB instances.
  • When you modify configurations of a MySQL DB instance associated with DDM, an exception may occur. After the modification, you need to click Synchronize DB Instance Data on the DDM instance details page to synchronize the change to DDM.

Syntax restrictions on DDL

Syntax restrictions on DML

Restrictions on database administration statements

Restrictions on advanced SQL functions


Use Cases



Traditional industry 


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