Security
Security for SQL Server has always had a "defense-in-depth" strategy. This means that you start with the outermost layer of the system and ensure that you have two areas identified and mitigated for each layer: Access and Authentication. Access has to do with what a user or process (called a Principal) can see and work with (called Securables), and authentication is about verifying the Principal's credentials.
SQL Server has a very secure security environment, allowing you to control and monitor very fine-grained access to the platform, the databases, and the database objects. It supports working with Active Directory accounts, certificates, and also SQL Server-defined and -controlled user accounts. You can also audit and monitor all security activities, and the security profiles can reach the highest government levels of security.
In an SQL Server 2019 big data cluster, it gets a bit more complex, since you're dealing not only with SQL Server, but...