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PROFESSIONAL-DATA-ENGINEER · Question #342

You have two projects where you run BigQuery jobs: - One project runs production jobs that have strict completion time SLAs. These are high priority jobs that must have the required compute…

The correct answer is B. Create two reservations, one for each of the projects. For the SLA project, use an Enterprise Edition with a baseline of 300 slots and enable autoscaling up to. Option B is correct because the SLA project requires an Enterprise Edition reservation with a 300-slot baseline (covering its constant usage) and autoscaling to handle the occasional 500-slot spike - while the ad-hoc project should be left on on-demand (pay-per-byte) billing…

Submitted by omar99· Mar 30, 2026Designing data processing systems

Question

You have two projects where you run BigQuery jobs: - One project runs production jobs that have strict completion time SLAs. These are high priority jobs that must have the required compute resources available when needed. These jobs generally never go below a 300 slot utilization, but occasionally spike up an additional 500 slots. - The other project is for users to run ad-hoc analytical queries. This project generally never uses more than 200 slots at a time. You want these ad-hoc queries to be billed based on how much data users scan rather than by slot capacity. You need to ensure that both projects have the appropriate compute resources available. What should you do?

Options

  • ACreate a single Enterprise Edition reservation for both projects. Set a baseline of 300 slots. Enable autoscaling up to 700 slots.
  • BCreate two reservations, one for each of the projects. For the SLA project, use an Enterprise Edition with a baseline of 300 slots and enable autoscaling up to
  • CCreate two Enterprise Edition reservations, one for each of the projects. For the SLA project, set a baseline of 300 slots and enable autoscaling up to 500 slots.
  • DCreate two Enterprise Edition reservations, one for each of the projects. For the SLA project, set a baseline of 800 slots. For the ad-hoc project, enable

How the community answered

(52 responses)
  • A
    8% (4)
  • B
    71% (37)
  • C
    17% (9)
  • D
    4% (2)

Explanation

Option B is correct because the SLA project requires an Enterprise Edition reservation with a 300-slot baseline (covering its constant usage) and autoscaling to handle the occasional 500-slot spike - while the ad-hoc project should be left on on-demand (pay-per-byte) billing, meaning it should not be assigned to a slot reservation at all. In BigQuery, projects not assigned to a reservation default to on-demand pricing, which bills by bytes scanned rather than slot capacity.

A is wrong because combining both projects in a single reservation forces the ad-hoc project onto slot-capacity billing, violating the requirement to bill by data scanned.

C is wrong because it creates an Enterprise Edition reservation for the ad-hoc project - again, assigning it to any reservation means slot-based billing, not per-byte billing.

D is wrong because setting a static baseline of 800 slots for the SLA project wastes money; since the spike is only occasional, autoscaling from a 300 baseline is the cost-efficient and correct approach.

Memory tip: "Reserved = billed by slots, On-demand = billed by bytes." Any project assigned to a reservation loses on-demand billing - so if a requirement says "bill by data scanned," that project must have no reservation assignment.

Topics

#BigQuery Reservations#BigQuery Pricing#Autoscaling#Resource Allocation

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