Thank you for pointing us to Gizzard. Based on our understanding of Gizzard’s blog, we would like to highlight the key differences as follows.

The key advantage of Gizzard is that it divides the data into key ranges and treats it as a shard. If a shard is too hot, it can dynamically adjust the size of the range. Gizzard also acts as a traffic routing layer that sends requests to the right server and coordinates data replication.

Shard Manager (SM) uses fixed-size shards and uses shard migration to reduce load on hot servers. Unlike Gizzard, SM focuses on being a control plane service and client traffic does not flow through SM. That functionality is delegated to Facebook’s separate traffic routing framework. SM supports more generic sharding applications and uses add/drop shard protocol to coordinate state migration. Gizzard focuses on data store applications and requires write operations to be idempotent and commutative in order to support state migration.