We are happy to announce General availability of Business Critical tier in Azure SQL Managed Instance  architectural model built for high-performance and IO demanding databases. After 5 months of public preview period Azure SQL Managed Instance Business Critical Service tier is generally available. Azure SQL Managed Instance Business Critical tier is built for high performance databases... Read more

https://blogs.msdn.microsoft.com/sqlserverstorageengine/2018/12/04/azure-sql-managed-instance-business-critical-tier-is-generally-available/