What Traversal rents

In week eight, Sam blocks out an afternoon and opens a spreadsheet titled RACE DAY SIZING, the same spreadsheet as last year with the numbers grown, and goes shopping for arithmetic. Three columns. One guess each.

Every machine Traversal rents is a bundle of three resources, and Sam’s job is to guess race day’s appetite for each. The first is the CPUConcept · lights on your mapCPUThe central processing unit: the part of the computer that executes instructions and does the arithmetic, billions of times a second. Everything else exists to feed it work and hold its results., the part that actually does things, billions of small things a second. Recording a crossing costs a little of it, computing a projected finish costs rather more, and a quarter of a million timing events in a four-hour window is, before it is anything else, a CPU bill.

Second of the three: memory / RAMConcept · lights on your mapmemory / RAMThe computer’s fast temporary workspace, holding whatever is actively being worked on. Its contents are normally lost when the power goes., the workbench: fast, close, and wiped clean when the power goes. The third is storage / diskConcept · lights on your mapstorage / diskWhere files and data are kept for the long term: bigger than memory, slower to reach, and it survives the power going off., the cabinet under the bench: slower, vaster, and it survives the night. Ten years of race history sits on storage; the quarter-million timing events of race morning will each sit in memory for half a second on their way to being written down properly, and the difference between those two sentences is the entire distinction. Bench. Cabinet.

The two words engineers actually say

That bench-versus-cabinet split has formal names worth recognising. What survives is persistentRecognition — just know it existspersistentIntended to remain available over time: the cabinet. The word to reach for around databases and storage.; what is willing to vanish is ephemeralRecognition — just know it existsephemeralTemporary, gone when the process or machine stops: the desk. The word for anything a system is designed to lose without grief.. A cache is ephemeral by design, which is why losing one is a slow afternoon and not an incident. The registrations table is persistent, which is why scene nineteen’s promises exist at all. Half of infrastructure design is deciding, resource by resource, which of these two words it deserves.

Sam’s spreadsheet lands on numbers with a healthy margin and a note reading validate under load, which is a promise to a later scene. The renting itself, whose building, whose meter, what happens when the guess is wrong, is an Act III problem, and Sam knows it.

Meanwhile, out on the course of this story, the smallest computer of all has been waiting eight weeks for its close-up.