Cloud cost
BigQuery slot
A unit of query-processing capacity in BigQuery. On-demand queries draw from a shared pool billed by bytes scanned; an Editions reservation buys dedicated slots billed by slot-hour instead.
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Definition
On-demand, BigQuery's default pricing, doesn't charge for slots directly — it bills per TiB of data a query scans, and slots are allocated behind the scenes. Editions flips that: you reserve a baseline number of slots (with an autoscaling ceiling above it), and pay for that capacity by the hour whether or not it's fully used.
Which one is cheaper depends on scan volume. Below a certain amount of data scanned per month, on-demand wins; above it, a slot reservation does. The two cost the same at a specific crossover point.
Where it shows up
BigQuery's billing model shows up directly in the console's billing settings: on-demand pricing charges per tebibyte of data scanned, with slot allocation handled behind the scenes, while an Editions reservation shows a reserved slot count and an autoscaling ceiling above it, billed by the hour instead.
What makes it expensive
A common expensive habit is staying on-demand well past the volume where a slot reservation would cost less, or reserving slots before scan volume justifies it. There is a published crossover point where the two models cost the same. Knowing which side of it your monthly scan volume sits on is the entire decision.
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