What was the criteria used to determine using Mysql for recording impressions and actions

[pareshshah]

Since Wasabi already uses Cassandra data store to record the assignments, we would have also like the impressions and actions to be also recorded there. Specially knowing that there will be many calls to this and mysql being relational DB would be slow compared Cassandra from the "write" scalability perspective.

Any thoughts behind choosing MySql for impressions/actions will be greatly appreciated.