Cloud cost
BigQuery slot
A unit of query-processing capacity in BigQuery. On-demand queries use a shared pool billed by bytes scanned. An Editions reservation buys dedicated slots billed by the slot-hour.
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Definition
On-demand is the BigQuery default. It does not charge for slots directly. It bills per TiB of data that a query scans, and it allocates slots behind the scenes. Editions flips this. You reserve a baseline number of slots, with an autoscaling ceiling above it. You pay for that capacity by the hour, whether or not you fully use it.
Which one is cheaper depends on scan volume. Below a certain amount of data scanned each month, on-demand wins. Above it, a slot reservation wins. The two cost the same at one crossover point.
Where it shows up
BigQuery's billing model shows in the console's billing settings. On-demand pricing charges per tebibyte of data scanned, and slot allocation happens behind the scenes. An Editions reservation shows a reserved slot count with an autoscaling ceiling above it. That capacity bills by the hour.
What makes it expensive
Two habits cost money. One is to stay on-demand well past the volume where a slot reservation would cost less. The other is to reserve slots before scan volume justifies them. A published crossover point exists where the two models cost the same. Know which side of it your monthly scan volume sits on. That is the whole decision.
Related
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- Auto-suspend / resume minimum
- Bytes scanned & partition pruning
- Time Travel & Fail-safe
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