One of the neat things about aurora is there is a very small slave lag between the primary and read replicas. If you only have a single thread doing replication

One of the neat things about aurora is there is a very small slave lag between the primary and read replicas. If you only have a single thread doing replication then you can easily have a situation where a multi-cpu master can get ahead of a slave only using a single thread. Lazily materializing the pages gives aurora 'parallel replication' for free. I think Mysql supports parallel replication now but I think it is limited if transactions conflict [https://mariadb.com/kb/en/library/parallel-replication/ https://mariadb.com/kb/en/library/parallel-replication/]. Another thing I noticed with Aurora is the incremental cost of storage for Aurora is extremely cheap compared to the cost of storage in EBS or the cost of storage if you used instance storage in EC2. The Aurora storage is 0.1/GB but this is replicated 6 times which is more than EBS and EBS costs the same 0.1/GB. This also might be why no-one is going to build a similar system to Aurora. It will be hard to sell something like Aurora to cloud users because the storage costs are going to more than what EC2 charges.