1. Key-Value Store

2. Key-Value Store
Built to hold millions/billions of records accessible solely by a single key field.
The key is a unique identifier used to locate the data rapidly.
The value is the data itself, the format varies. Often the value is just a string of bytes and the application needs to interpret this data. In some implementations the value is self-describing (like JSON).
The main characteristic of a key-value store is the fact that every value (data item) must be associated with a unique key, and that retrieving that value by supplying the key must be very fast.

3. Examples of Key-Value Stores
Dynamo DB is used to support Amazon's AWS/SDK platforms and can be used in cloud computing operations.
Open Source Voldemort
Redis key-value cache and store
Apache's Cassandra (used by Facebook)

4. Voldemort
A table/collection/store in Voldemort does not have a schema, it holds a collection of self-describing items.
Each item consists of a number of (attribute, value) pairs, and attribute values can be single-valued or multivalued.
You specify an item in JSON, and Voldemort converts that to its internal representation.

5. Voldemort Primary Key
All tables have a name and a primary key. The primary key is the key and the item is the value for the Voldemort key-value store.
The primary key can be one of the following two types:
A single attribute: Voldemort uses this attribute as a hash index. Items are stored according to the hash value.
A pair of attributes: The first attribute is the hash index, and second attribute is used to order records with the same hash index. Often the first attribute is a unique identifier, and the second is a timestamp.

6. Voldemort Usage put "k1" "v1" put "k2" "v2" get "k1" getall "k1" "k2"
delete "k1"

7. What distinguishes Document Stores from Key-Value Stores?
1. Key-Value stores can't store self-describing data
2. Document stores don't have keys
3. Key-Value can do versioning
4. They are basically the same thing, next question.