Which of the following is/are a key-value data store?试题 14选择一项或多项：a.CouchDBb.Hbasec.Voldemortd.Hypertablee.Dynamof.MongoDB

To identify which options are key-value data stores, let's analyze each one:

1. CouchDB: Primarily a document store, but it does offer some key-value storage features. However, it is not classified strictly as a key-value store.

2. HBase: A column-family NoSQL database that is built on top of HDFS (Hadoop Distributed File System). While it supports key-value storage, it is not solely a key-value store and instead is designed for wide-column data.

3. Voldemort: A distributed key-value storage system. It is specifically designed to handle key-value pairs, making it a clear example of a key-value store.

4. Hypertable: A database modeled after Google Bigtable, which can store data in key-value pairs but is also considered a column-family store.

5. DynamoDB: A fully managed key-value and document database that offers high performance and scalability. It is a true key-value store.

6. MongoDB: Primarily a document database that stores data in flexible, JSON-like documents. While it has some key-value storage capabilities, it is not considered a key-value store.

Final Answer

The options that are key-value data stores are:

• b. HBase (partially, although it's not strictly a key-value store)
• c. Voldemort
• d. DynamoDB

Correct options based on strict definitions: c. Voldemort and d. DynamoDB.