Amazon DynamoDB is a fully managed proprietary NoSQL database service that supports key–value and document data structures and is offered by Amazon.com as part of the Amazon Web Services portfolio.
Dynamo had a multi-leader design requiring the client to resolve version conflicts and DynamoDB uses synchronous replication across multiple data centers for high durability and availability.
DynamoDB was announced by Amazon CTO Werner Vogels on January 18, 2012, and is presented as an evolution of Amazon SimpleDB.
DynamoDB differs from other Amazon services by allowing developers to purchase a service based on throughput, rather than storage. If Auto Scaling is enabled, then the database will scale automatically.
To prevent data loss, DynamoDB features a two-tier backup system of replication and long-term storage.
Each partition features three nodes, each of which contains a copy of that partition's data.
Each node also contains two data structures: a B tree used to locate items, and a replication log that notes all changes made to the node.
DynamoDB periodically takes snapshots of these two data structures and stores them for a month in S3 so that engineers can perform point-in-time restores of their databases.
Official website : http://aws.amazon.com/dynamodb/