A company runs MySQL on self-managed servers in an on-premises data center and wants to move to a managed AWS database service. Which migration approach should they use?

Replatform is the correct approach because it involves making some cloud-native optimizations without changing the core architecture. In this scenario, moving from self-managed MySQL to a managed AWS database service (like Amazon RDS for MySQL) means the application code interacting with the database generally remains the same, but the underlying database infrastructure is replaced with a managed service, reducing operational overhead. Rehost (lift-and-shift) would involve migrating the self-managed MySQL server as-is to an EC2 instance, which doesn't leverage the benefits of a managed database service. Repurchase means replacing the existing application or database with a new, cloud-native product, which isn't the primary goal here. Refactor would involve significant architectural changes to fully embrace cloud-native features, which is beyond simply moving to a managed database service.