Help me understand GCE Costs - Data transfer costs for GCE is new to me

[dheerajpanyam]

I am aware of GCE storage and compute costs plus network data transfer costs between GCE VMs assuming they are in different regions  , today I am saw a  SKU related to carrier peering and data transfer costs with GCE and i don't understand where it is coming from. We have a GCE VM connected to Atlas Mongo instance via VPC peering (Next JS app deployed on a GCE VM with MongoDB Atlas as a backend , is this cost attributed to this data transfer?

[francislouie]

Hi dheerajpanyam,

Welcome to Google Cloud Community!

Yes, the "carrier peering" costs you are seeing are likely associated with the data transfer between your GCE VM (via VPC peering) and MongoDB Atlas, particularly if they're located in different regions. In this kind of setup, Inter-region data transfer is utilized.

 Additionally, a relevant discussion on the Reddit forum. According to @elvis of Google Cloud Support:

There are a few possible reasons why you might be seeing this charge:

• Default VPC Network Routing: By default, Google Cloud routes outbound traffic from your project through its network and carrier peering partners to ensure reliable and efficient internet connectivity. This service might be reflected in your bill even if you haven't explicitly configured peering.
• Third-party Services: If you're using any third-party services within your project that communicate externally, they might be using carrier peering for their own data transfer, which could be reflected in your bill.

To get a more detailed breakdown, I'd recommend:

• Checking the VPC Flow Logs or  network egress or  charges from GCE for data leaving the Google Cloud environment.
• Reviewing MongoDB Atlas documentation on data transfer pricing, as they might charge differently based on the type of network connection you're using (e.g., public vs. private).

For further assistance, please consider reaching out to Cloud Billing support for more detailed guidance.

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[dheerajpanyam]

Thanks @francislouie for your answer. Sorry i forgot to mention one important information about the setup. I see a VPC networking peering connection in the GCP console between GCP and Mongo Atlas which i am assuming is a private connection in which case the egress costs won't apply , please correct me if i am wrong. 

[dheerajpanyam]

@francislouie  i realized we are also using Cloud Flare for caching content served from the applications deployed on the VMs, so it might not be Mongo charges since it uses VPC peering / private connection.