BigQuery Reservation API cost split into 2 projects

[JoyceF]

Hello,

could you please help me with this?

Issue Overview
*Project "ProjectA": This project holds the reservation slots (committed usage) that are purchased by joy. *It does not run any BigQuery (BQ) jobs, yet charges are visible under this project in the billing console.

*Project "ProjectB"- *This project uses the reservation slots purchased under "ProjectA" It has active BigQuery jobs running and shows charges for BQ usage in the billing console, even though it doesn’t own the reservation slots directly.

I have multiple projects, with reservation slots purchased under "ProjectA" Although no jobs are running under this project, charges still appear in the billing console. The project "ProjectB" uses those reservation slots but doesn't have direct reservations. Since jobs are running there, charges also appear in the billing console for this project.

Can you please help me because I am confused how costs are split.

Is it because of this?

*The cost of reserved slots is charged to the project where the slots were purchased, “ProjectA”. Does it mean that regardless of which project consumes the slots, the cost of the reservation itself remains with the purchasing project.

*When BigQuery jobs are run in “ProjectB”, the project utilizes the reservation slots purchased by “ProjectA”. If the reservation slots are sufficient, no on-demand charges should occur. The cost of slot utilization is not directly charged to “ProjectB” but other charges like storage etc.

Could you please confirm this?Your insights are highly appreciated. Thank you!

[ibaui]

Hi @JoyceF,

You're correct in your understanding of how BigQuery reservation costs are managed across projects. 

The cost of the reserved slots is always billed to the project that owns the reservation which in this case is ProjectA. This is fundamental to how BigQuery reservations work. The reservation is like a lease, and you pay for the lease regardless of how much you use the property (the slots).

If ProjectB runs a query and it successfully uses the slots from ProjectA's reservation, you should not see on-demand charges related to slot usage in ProjectB. ProjectB will still be billed for:

• Storage: Storing data in BigQuery (whether it's actively queried or not).
• Networking: Data egress charges (though these are often minimal).
• Any features not covered by reservations: Some advanced features might have separate pricing models that are not covered by reserved slots. You can check the BigQuery pricing documentation for details.

You can also refer to this document for more details on the fundamental concepts and a better understanding of BigQuery reservations.

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