Weighted traffic splitting allows you to gradually route a percentage of traffic to the new GKE application while still serving the majority of requests through the Compute Engine instance. This gradual transition minimizes risks and ensures seamless traffic distribution during migration.
Reference: Google Cloud - Traffic Splitting for Load Balancers

The correct answer is D. Create an instance template and a managed instance group. Configure two separate internal TCP/UDP load balancers for each protocol (TCP/UDP), and configure the client VMs to use the internal load balancers' virtual IP addresses.
This answer is based on the following facts:
Using multi-NIC VMs as network virtual appliances (NVAs) allows you to route traffic between different VPC networks1. You can use NVAs to implement custom network policies and security requirements.
Using an instance template and a managed instance group allows you to create and manage multiple identical NVAs2. You can also use health checks and autoscaling policies to ensure high availability and reliability of your NVAs.
Using internal TCP/UDP load balancers allows you to distribute traffic from client VMs to NVAs based on the protocol and port3. You can also use health checks and failover policies to ensure that only healthy NVAs receive traffic.
Configuring the client VMs to use the internal load balancers' virtual IP addresses allows you to simplify the routing configuration and avoid manual intervention4. You do not need to create static routes or update them when NVAs are added or removed.
The other options are not correct because:
Option A is not suitable. Creating the VMs in the same zone does not provide high availability or failover. Using static routes with IP addresses as next hops requires manual intervention when NVAs are added or removed.
Option B is not optimal. Creating the VMs in different zones provides high availability, but not failover. Using static routes with instance names as next hops requires manual intervention when NVAs are added or removed.
Option C is not feasible. Creating an instance template and a managed instance group provides high availability and reliability, but using a single internal load balancer does not support both TCP and UDP protocols. You cannot define a custom static route with an internal load balancer as the next hop.

This answer meets the requirement of configuring one connection as Active for both ingress and egress traffic, and enabling automatic failover to the passive connection in case of failure. The reason is:
* The advertised route priority is a value that Cloud Router uses to set the route priority when advertising routes to your on-premises router. The lower the value, the higher the priority1. By setting the advertised route priority as 200 for the active connection, you ensure that it has a higher priority than the passive connection, which has the default value of 1001. This way, your on-premises router will prefer the routes from the active connection over the passive one for ingress traffic.
* The MED (Multi-Exit Discriminator) is a value that your on-premises router uses to indicate its preference for receiving traffic from Cloud Router. The lower the value, the higher the preference2. By advertising a lower MED on the active connection from your on-premises router, you ensure that Cloud Router will prefer sending traffic to the active connection over the passive one for egress traffic.
* If the active connection fails, Cloud Router will stop receiving routes from it and will start using the routes from the passive connection for egress traffic. Similarly, your on-premises router will stop receiving routes with priority 200 from the active connection and will start using the routes with priority
100 from the passive connection for ingress traffic. This achieves automatic failover without any manual intervention.
Option A is incorrect because setting the advertised route priority > 10,200 on the active connection would deprioritize it globally in your VPC network, which is not what you want1. Option B is incorrect because advertising a lower MED on the passive connection would make Cloud Router prefer sending traffic to it over the active one, which is not what you want2. Option D is incorrect because setting the advertised route priority as 200 for both connections would make them equally preferred by your on-premises router, which is not what you want1.
:
Update the base route priority | Cloud Router | Google Cloud
Configuring BGP sessions | Cloud Router | Google Cloud

The core requirement is to move a massive amount of sensitive data (900 TB daily) directly between Google Cloud and AWS with highest performance, lowest latency, and in-transit encryption, while maintaining existing on-premises connectivity.
Option A directly addresses this by recommending Cross-Cloud Interconnect with 100 Gbps circuits between AWS and Google Cloud. Cross-Cloud Interconnect is designed for high-throughput, low-latency connectivity between different cloud providers. The crucial part for sensitive data and encryption is "configuring IPsec encryption on both sides of the connection," as Cross-Cloud Interconnect itself provides a private path but not inherent encryption. Cloud Router and BGP are essential for dynamic route exchange. This option focuses on the direct cloud-to-cloud path for the high volume data transfer.
Options B and C involve upgrading the existing connections to the on-premises data center and routing all traffic through it. While this could work, it adds an unnecessary hop and likely higher latency for direct cloud- to-cloud traffic, making it less optimal for "highest performance and lowest latency" between clouds.
Additionally, removing existing 10Gbps circuits is not necessary and might impact the existing topology if not done carefully.
Option D suggests MACsec, which provides Layer 2 encryption. While good for physical security, for data replication services with sensitive data, IPsec (Layer 3 encryption) is more commonly used and flexible for end-to-end encryption across a routed network, and is typically preferred for data integrity and confidentiality over an IP network. Also, MACsec requires specific hardware support and is typically implemented at the interconnect termination points, not necessarily end-to-end for an application. Given the sensitive nature of the data and the large volume, IPsec provides the necessary transport-level encryption.
Exact Extract:
"Cross-Cloud Interconnect enables direct connectivity between your Google Cloud VPC networks and other cloud provider networks. It provides high-bandwidth, low-latency connections, ideal for large-scale data transfers between clouds."
"For sensitive data, you can implement IPsec VPN tunnels over Cross-Cloud Interconnect connections to provide encryption in transit. This ensures data confidentiality and integrity over the dedicated interconnect."
"Cloud Router dynamically exchanges routes between your Google Cloud VPC network and your other cloud network over the Cross-Cloud Interconnect connection using BGP."Reference: Google Cloud Cross-Cloud Interconnect Documentation - Overview, Encryption options for hybrid connectivity