Ensuring High Availability in DynamoDB

Let's discuss some ways in which we can keep our database highly available.

Write availability

Our database follows a model where tables are partitioned, and partitions are replicated. A set of replicas of the same partition is called a replication group. Partitions use a leader election based on Multi-Paxos to elect a leader replica. This leader replica is responsible for serving to write requests—it adds the new entry to the write-ahead log and indexes in its memory. Later, this leader shares its write-ahead log and tree index with other partitions in the replication group. This is possible if enough healthy replicas (two-thirds) are available to form a write quorum. Write consistency in our distributed database depends on the ability of the network to maintain healthy ...