1.亚马逊极光：
它是来自 Amazon Web Services 的完全托管的关系数据库引擎，与 PostgreSQL 和 MySQL 兼容。它比标准 MySQL 数据库快五倍，比标准 PostgreSQL 数据库快三倍。 Aurora 的特点是分布式、容错和自愈存储系统。
2. 第四维(4D)：
第四维是由 Laurent Ribardière 开发的关系数据库管理系统和 IDE。 4D 可以作为服务器运行，以便多个客户端可以管理单个数据库。 4D 创建于 1984 年，并于 1987 年为 Macintosh 稍微推迟了公开发布。它是一个具有集成数据库管理系统的应用程序开发环境。
Amazon Aurora 和 4D 的区别：
| AMAZON AURORA | 4D |
|---|---|
| It is developed by Amazon in 2015. | It is developed By 4D, Inc in 1984. |
| It is a MySQL and PostgreSQL compatible cloud service by Amazon. | It is a hosted simple database service by Amazon, with the data stored in the Amazon Cloud. |
| It supports predefined data types such as float or date. | It does not support predefined data types such as float or date. |
| Immediate Consistency is used to ensure consistency in a distributed system. | Eventual Consistency and Immediate Consistency is used to ensure consistency in a distributed system. |
| It is available as a cloud service. | It is not available as a cloud service. |
| The partitioning can be done with horizontal partitioning. | There is no Partitioning method. |
| It supports SQL query language. | It does not support the SQL query language. |
| It provides the concept of Referential Integrity. Hence, no Foreign Keys. | It does not provide the concept of Referential Integrity. Hence, no Foreign Keys. |
| APIs and other access methods supported are ODBC, RESTful HTTP API and SOAP web-services. | APIs and other access methods supported are JDBC and ODBC. |