Inconsistent API errors make clients hard to write. Problem Details give ASP.NET Core a standard shape for HTTP failures, from expected endpoint errors to global exception handling.

Database transactions ensure multiple operations succeed or fail together. EF Core wraps SaveChanges in an implicit transaction, with explicit transactions and savepoints for more complex flows.

You do not need a class library per layer to follow Clean Architecture. One ASP.NET Core project, clear namespaces and NsDepCop or architecture tests can enforce the same dependency rules as a multi-project solution.