What Is a Slot?

A slit or other narrow opening, especially one for receiving something. A person might say, “I can slot you in at 2 p.m.”

In computer technology, a slot is an area on a motherboard where an expansion card can be plugged in. A slot might also refer to a specific memory location on a computer system. The term is sometimes used as a synonym for an ISA or PCI (peripheral component interconnect) slot, but it can also describe any type of expansion port on a computer.

The first slot machine was created by Sittman and Pitt in 1891, and featured a series of drums with a total number of poker hands that could be lined up to win credits. In modern video slot machines, a player inserts cash or, in the case of ticket-in/ticket-out devices, a paper ticket with a barcode into a slot on the machine to activate a reel set that spins to produce symbols. Each symbol has a value based on the pay table, which is listed on the face of the machine or, for electronic machines, in a help menu.

In the context of BigQuery, a slot is a unit of capacity that lets you run a limited number of concurrent queries within a given time period. The more slots you purchase, the more concurrent queries you can run. When you use the capacity-based pricing model, you pay for your slots every second that they’re deployed.