You plan to deploy an Azure VPN gateway in a subscription that contains a virtual network and require 90 Site-to-Site VPN connections. The design must keep those Site-to-Site connections available if a single Azure datacenter fails and must minimize costs. Which VPN gateway SKU should you choose?

VpnGw4AZ is the correct choice because it supports up to 100 Site-to-Site VPN tunnels and offers zone-redundancy, ensuring high availability even if a single Azure datacenter fails. This meets both the connection count and resilience requirements. VpnGw1AZ and VpnGw2AZ do not support 90 Site-to-Site connections (they support 30 and 50 respectively). While VpnGw5AZ also supports zone-redundancy and more than 90 connections (up to 1000), it is significantly more expensive than VpnGw4AZ, failing the cost minimization requirement.