A company runs an ecommerce application on premises on Microsoft SQL Server.

The requirement combines two key goals: reduce post-migration database administration/maintenance cost and minimize application rewrites for an existing Microsoft SQL Server application that relies heavily on T-SQL and stored procedures. Amazon Aurora PostgreSQL-Compatible with Babelfish is designed for this exact migration pattern: it helps applications written for SQL Server to run with reduced code changes by providing compatibility for commonly used SQL Server semantics, including T-SQL constructs, procedural logic, and SQL Server-style connectivity patterns (depending on feature usage). Aurora itself is a managed database service that reduces operational overhead compared to self-managed databases by offloading tasks such as provisioning, patching (within service capabilities), backups, and high availability patterns.

Option C (RDS for SQL Server) would indeed minimize rewrites because it keeps the engine the same, but it typically does not optimize operating costs as effectively as migrating off commercial SQL Server licensing/edition costs; it also keeps you on the same engine family, which often carries higher license implications and may not meet the “minimize operating costs” intent as strongly as moving to Aurora PostgreSQL with Babelfish. Option B is not suitable because Redshift Spectrum is for analytics over data in S3, not for running an OLTP ecommerce database with stored procedures. Option D is also a mismatch: EMR is for big data processing frameworks, not a relational OLTP database replacement for SQL Server.

Therefore, A best balances lower ongoing operational cost with reduced refactoring effort by using Aurora’s managed capabilities while leveraging Babelfish to ease SQL Server-to-PostgreSQL migration friction.