Etsy - MySQL Sharding

Below is the Esty architecture and how Etsy is handling over 1.5 billion page views per month and 15TB stored data.  The interesting part is that it is based on MySQL.

Extensive sharding is used for partitioning data.  Important concepts include building a database to handle shard_id look ups (user_id to shard_id, group_id to shard_id), and shard migration

The Etsy Shard Architecture: Starts With S and Ends With Hard from jgoulah