Google Cloud offers two network service tiers: Premium and Standard.

Premium Tier: Uses Google's global, low-latency, and highly reliable backbone for most of the traffic's route, resulting in minimal latency. This is essential for latency-sensitive financial production systems.

Standard Tier: Uses Google's network for part of the route and then public ISPs. It offers a lower cost compared to Premium Tier but potentially higher latency. This is suitable for non-critical, cost-sensitive development workloads.

The optimal design is to use two separate VPCs (or at least different networking setups if using Shared VPC), with the Premium Tier for production (minimizing latency) and the Standard Tier for development (minimizing cost).