1.卡桑德拉(Cassandra)：
Cassandra是一个免费的开放源代码的分布式宽列存储NoSQL数据库管理系统。它由Apache Software Foundation开发，最初于2008年7月发布。Cassandra旨在处理许多商用服务器上的大量数据，提供高可用性而没有单点故障。
2. CouchDB：
Apache CouchDB是面向开源文档的NoSQL数据库，它使用多种格式和协议来存储，传输和处理其数据，它使用JSON来存储数据，使用JavaScript作为其使用MapReduce的查询语言以及使用HTTP作为API。它由Apache Software Foundation开发，最初于2005年发布。它是用Erlang编写的。 Cassandra和CouchDB之间的区别：
| S.NO. | Cassandra | CouchDB |
|---|---|---|
| 1. | Developed by Apache Software foundation and released on July 2008. | Developed by Apache Software Foundation and initially released in 2005. |
| 2. | Cassandra is written in Java language. | CouchDB is written in Erlang language. |
| 3. | The primary database model for Cassandra is Wide Column Store. | The primary database model for CouchDB is Document Store. |
| 4. | Cassandra supports predefined datatypes such as float, date, number, etc. | In CouchDB there is no predefined datatypes. |
| 5. | Secondary indexes in Cassandra is restricted. | CouchDB does not supports Secondary indexes. |
| 6. | Cassandra have SQL supports i.e it supports some SQL statements like DML, DDL, SELECT, etc. | CouchDB does not supports SQL. |
| 7. | Cassandra supports Selectable Replication Factor replication method. | CouchDB supports Master-Slave Replication and Master-Master Replication replication methods. |
| 8. | Cassandra provides both Eventual Consistency and Immediate Consistency methods to ensure consistency in a distributed system. | CouchDB provides Eventual Consistency method to ensure consistency in a distributed system. |
| 9. | Server operating systems for Cassandra are BSD, Linux, OS X, Windows. | Server operating systems for CouchDB are Android, BSD, Linux, OS X, Solaris and Windows. |
| 10. | Famous companies like GitHub, Hulu, Instagram, Reddit, The Weather Channel, etc uses Cassandra. | Famous companies like Akamai Technologies, Hothead Games, Inc., GenCorp Technologies, Vivint Solar, etc uses CouchDB. |