What race day costs

Thursday, 10 a.m., the big room. Dana on one side, Sam on the other, Finn and Priya in between, one agenda item: race day, and what it costs.

This meeting has a vocabulary, and learning to follow it is learning to follow every architecture argument you will ever sit in. The axes come first. scalabilityConcept · lights on your mapscalabilityHow well a system handles growth: more users, more data, more traffic. A scalable design grows capacity without redesign; an unscalable one must be rebuilt at each new size. is whether growth breaks the design. Traversal’s question is seasonal and sharp: the system must be twenty times bigger on Sunday than on an ordinary Tuesday, and back to ordinary by the Wednesday after.

reliabilityConcept · lights on your mapreliabilityWhether the system does the correct thing, consistently: no lost entries, no double charges, no wrong answers. Distinct from availability: reliability is being right, availability is being present. is whether the answers are right, and availabilityConcept · lights on your mapavailabilityWhether the system is up and answering, measured in nines: 99.9% allows roughly nine hours of downtime a year, 99.99% allows about fifty-three minutes, and each extra nine costs roughly ten times the engineering. is whether there are answers at all. The distinction sounds pedantic until you watch it carry a decision. A leaderboard that is up but wrong is available and unreliable. A timing pipeline that pauses rather than record a doubtful split is choosing reliability over availability, on purpose, and Sunday will make exactly that choice.

The axis nobody puts on a poster

And underneath the whole hour runs costConcept · lights on your mapcostWhat a design spends: the cloud meter, third-party fees, and the one beginners forget, engineer time. “That is an expensive way to buy a millisecond” is a cost argument winning.. The cloud meter, the vendor fees, and the spend nobody puts on a slide, which is engineer attention. Sam’s doubled headroom costs real money per hour of Sunday; Dana asks the number out loud; the number is fine — the asking is the point. Every axis in this meeting can be bought up at the price of some other axis, and the meeting exists so the buying happens on purpose.

An hour in, nobody has said a number about speed. That is the second half of the review, and it has the two most confused words in the industry in it.