To assign specific Compute Engine instances in your Managed Instance Group (MIG) for handling read-heavy and write-heavy database queries, what would be the most effective method?

*The optimal solution for segregating read-heavy and write-heavy database queries across different Compute Engine instances in a Managed Instance Group is to utilize multiple instance templates within the same MIG, each configured with per-instance configurations. This approach allows the assignment of specific machine types within the same MIG tailored to the query loads - one for read-heavy operations and another for write-heavy tasks. Such a setup leverages GCP's native capabilities to efficiently distribute workload-specific queries to appropriate instances. Other methods, such as target pools, URL maps, or custom application logic, either don't support query-based traffic direction or add unnecessary complexity. Separate MIGs combined with Cloud Functions for query distribution also introduce additional complexity and management overhead, making them less ideal for this scenario.*