Network Cost Optimization: FinOps for Networking

Networking costs in Google Cloud are the silent budget killer. Compute costs are obvious—you see the VM, you see the price. But network egress charges, Cloud NAT processing fees, and Interconnect port costs hide in the margins of your invoice, growing quietly until someone in finance asks, “Why is our cloud bill 40% higher than projected?” The answer is almost always network egress.

Understanding network cost is not just a FinOps exercise—it is an architecture exercise. The cheapest network is the one where traffic stays close to its origin, crosses the fewest boundaries, and uses the most efficient path available.

The Egress Cost Model
What Is Free
  1. Ingress: All traffic entering Google Cloud is free. Always.
  2. Intra-zone traffic: Traffic between VMs in the same zone is free.
  3. Traffic to most Google services: Using Private Google Access to reach Cloud Storage, BigQuery, etc., within the same region incurs no egress charges.
What Costs Money
  1. Inter-region egress: Traffic from us-central1 to europe-west1 is charged per GB.
  2. Internet egress: Traffic leaving Google Cloud to the public internet is charged per GB, with the rate depending on the network tier (Premium vs. Standard) and destination.
  3. Inter-zone egress: Even within the same region, traffic between different zones incurs a small per-GB charge.

The most impactful cost optimization is often the simplest: co-locate your compute and data in the same zone whenever possible.

Interconnect vs. VPN: The Cost Comparison
Interconnect
  1. Monthly port fee (e.g., ~$1,700/month for a 10 Gbps Dedicated Interconnect).
  2. VLAN attachment fee.
  3. Egress to on-premises through Interconnect is significantly cheaper than internet egress. This is the key financial argument for Interconnect—if you move large volumes of data back to on-prem, the reduced egress rate pays for the Interconnect.
VPN
  1. Per-tunnel-per-hour charge (~$0.075/hour per tunnel).
  2. Egress through VPN is charged at standard internet egress rates.
  3. For low-bandwidth connections, VPN is cheaper. For high-bandwidth, Interconnect wins.
Cloud NAT Costs

Cloud NAT charges for both the gateway itself and the data processed through it. The gateway fee is per-hour. The processing fee is per-GB. At scale, the processing fee dominates.

  1. Optimization: Avoid routing traffic through NAT when unnecessary. If a service supports Private Google Access (e.g., Cloud Storage), use PGA instead of NAT to reach it—PGA is free.
  2. Avoid over-provisioning NAT IPs: Each IP incurs a cost. Use Dynamic Port Allocation to maximize efficiency per IP.
Flow Logs and the Logging Tax

VPC Flow Logs are invaluable for diagnostics, but they are expensive at full sample rate. Every log entry is ingested by Cloud Logging, which charges per volume.

  1. Optimization: Set the sample rate to 0.5 or lower for subnets with high traffic.
  2. Aggregation Interval: Use 15-minute intervals instead of 5-second intervals for non-critical subnets.
  3. Exclusion Filters: Exclude known-good traffic patterns from ingestion to reduce log volume.
Load Balancer Costs
  1. Forwarding Rule charge: Per-hour fee for each forwarding rule.
  2. Data processing charge: Per-GB fee for data processed through the LB.
  3. Optimization: Combine multiple services behind a single LB using URL Maps instead of deploying separate LBs per service.
Putting it Together: A Pro-Engineer View

Imagine you receive your company’s cloud bill and find $12,000 in unexpected network charges. You investigate: $5,000 is internet egress from a data export job that could have used Interconnect. $3,000 is Cloud NAT processing for pods that were calling Cloud Storage—which could have used PGA for free. $2,000 is VPC Flow Logs at full sample rate on all 50 subnets—reducing the sample rate to 0.3 saves 70%. $2,000 is five separate load balancers that could have been consolidated into one with URL Maps. You implement these changes. Next month’s bill drops by $9,000. That is FinOps for networking—not cutting features, but routing money as efficiently as you route packets.

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