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Difficulty: Very hardOptimizing Network Performance and Latency

A financial analytics enterprise operates a hybrid transactional system. The on-premises transactional databases continuously replicate ledger data to a multi-region AWS environment containing VPCs in `us-east-1` (primary) and `us-west-2` (secondary). The hybrid network topology consists of a 10 Gbps AWS Direct Connect connection with a Transit Virtual Interface (VIF) terminated at a Direct Connect Gateway (DXGW). The DXGW is associated with an AWS Transit Gateway (TGW) in `us-east-1`, which is peered with a Transit Gateway in `us-west-2` to facilitate inter-region connectivity.

During peak transaction processing periods, the operations team identifies three critical issues:
1. Significant latency and packet drops occur when replicating transaction logs from the on-premises database to the Amazon RDS PostgreSQL databases in `us-west-2`. The replication traffic currently transits from on-premises to the `us-east-1` TGW, and then over the inter-region TGW peering connection.
2. The analytics engine VPCs in both AWS regions must resolve internal microservice endpoints hosted in a shared service VPC in `us-east-1` via a Route 53 Private Hosted Zone (PHZ) named `internal.analytics.local`. Currently, instances in `us-west-2` experience persistent name resolution failures.
3. For outbound compliance reporting traffic, the `us-east-1` VPC routes all internet-bound traffic through a single NAT Gateway located in a public subnet in Availability Zone `us-east-1a`. During periods of transient AZ degradation, instances in other AZs experience severe connectivity latency.

Which of the following actions should the Solutions Architect recommend to optimize the hybrid network performance, reduce latency, and resolve the connectivity and DNS resolution issues? (Select TWO.)

  1. Configure the on-premises routers and the AWS Direct Connect Transit Virtual Interface (VIF) to support a Maximum Transmission Unit (MTU) of 8500 bytes, ensuring the path matches the maximum MTU supported by AWS Transit Gateway to prevent packet fragmentation.Answer
  2. Associate the Route 53 Private Hosted Zone `internal.analytics.local` with the VPCs in both `us-east-1` and `us-west-2` regions to enable local DNS resolution, and deploy a dedicated NAT Gateway in each Availability Zone utilized by the `us-east-1` VPC to eliminate inter-AZ transit latency.Answer
  3. C
    Configure the Direct Connect Gateway to route VPC-to-VPC traffic directly between the `us-east-1` and `us-west-2` VPCs, bypassing the Transit Gateway peering connection to reduce inter-region replication latency.
  4. D
    Create a Route 53 Resolver Inbound Endpoint in `us-west-2` to host the `internal.analytics.local` Private Hosted Zone, and route all outbound internet traffic from `us-east-1` through a single NAT Gateway in `us-east-1a` to centralize traffic and minimize NAT gateway costs.
  5. E
    Deploy a pre-warmed Application Load Balancer in front of the database replication endpoints to manage traffic spikes, and configure Route 53 Resolver outbound endpoints in `us-west-2` to forward all DNS queries for `internal.analytics.local` to the inbound endpoints in `us-east-1`.

Answer

To optimize network performance, replication latency, and DNS resolution, the architect must configure the MTU to 8500 bytes on both the on-premises routers and the Transit VIF to match the maximum MTU supported by AWS Transit Gateway and prevent packet fragmentation. Additionally, the Private Hosted Zone must be associated with the VPCs in both regions to enable local DNS resolution, and a NAT Gateway must be deployed in each Availability Zone of the us-east-1 VPC to eliminate cross-AZ latency and single points of failure.
The correct solution addresses path MTU, DNS resolution, and local routing issues. First, configuring the MTU to 8500 bytes (Jumbo Frames) on the Direct Connect Transit VIF and on-premises routers aligns the network path with the maximum MTU supported by AWS Transit Gateway, which eliminates packet fragmentation and improves replication throughput. Second, associating the Private Hosted Zone with the VPCs in both regions ensures private DNS queries resolve natively within each VPC. Finally, deploying a NAT Gateway in each Availability Zone avoids inter-AZ network paths for internet-bound traffic, removing cross-AZ latency and providing resilience.

Step-by-Step Solution

1
Configure MTU size of 8500 bytes on the Direct Connect Transit Virtual Interface and on-premises routers.
Path MTU matches the AWS Transit Gateway maximum MTU for VPC/Direct Connect attachments.
This prevents IP packet fragmentation and the associated CPU overhead, eliminating replication latency spikes.
2
Associate the Route 53 Private Hosted Zone with the VPCs in both us-east-1 and us-west-2.
Instances in us-west-2 can resolve internal.analytics.local domain names locally.
Route 53 Private Hosted Zones must be explicitly associated with all VPCs that require local DNS resolution.
3
Deploy a NAT Gateway in each active Availability Zone of the us-east-1 VPC and update the respective route tables.
Outbound internet traffic stays within its local AZ.
This avoids cross-AZ transit latency, reduces data transfer costs, and prevents a single AZ outage from disabling outbound traffic for the entire VPC.

Key Concept

Path MTU alignment, multi-region Private Hosted Zone association, and Availability Zone-redundant NAT Gateway architectures.
Estimated Time:4m 0s
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Topics

Optimizing Network Performance and Latency