Database Reference
In-Depth Information
then that means that the replicas are out of sync, and then you can compare the next child
nodes and find out the actual discrepancy.
Each DynamoDB node maintains a Merkle tree for each and every key range it has. Doing
this, it allows DynamoDB to check whether certain key ranges are in sync or not. If it
finds any discrepancy, then child-wise traversal is done to find the cause of the discrep-
ancy, as shown in the following diagram:
The preceding diagram shows how two nodes in a DynamoDB cluster form Merkle trees
and compare hashes. This technique of replica synchronization is the same in Cassandra
and Riak as well. You can read more about Merkle trees at
http://en.wikipedia.org/wiki/
