In most production OpenStack installations, you want the backing metadata store to be highly available. For this, the de facto standard has become MySQL+Galera. In order to help you meet this basic use case even better, I will introduce you to the brand new native MySQL HA solution called MySQL Group Replication. This allows you to easily go from a single instance of MySQL to a MySQL service that's natively distributed and highly available, while eliminating the need for any third party library and implementations.
If you have an extremely large OpenStack installation in production, then you are likely to eventually run into write scaling issues and the metadata store itself can become a bottleneck. For this use case, MySQL NDB Cluster can allow you to linearly scale the metadata store as your needs grow. I will introduce you to the core features of MySQL NDB Cluster--which include in-memory OLTP, transparent sharding, and support for active/active multi-datacenter clusters--that will allow you to meet even the most demanding of use cases with ease.