This is a post in the SQL Interview series. These aren't trick or gotcha questions, they're just questions designed to scope out a candidate's knowledge around SQL Server and Azure SQL Database.
Many applications connect to SQL Server databases with users that are members of the db_datareader and/or db_datawriter roles?
Why should you avoid using those roles?
db_datareader and db_datawriter are fixed database roles that were provided for convenience. They aren't a good option from a security perspective.
Whenever you add a user (or group) to any fixed role, you are assigning them a collection of permissions. By definition, that list of permissions will need to include at least all the permissions they require.
However, invariably when you use fixed roles, you are also assigning additional permissions or access to objects that aren't required.
A more secure solution is to create a role and grant it only the permissions that are required, and then assign the user (or group) to that new role.