Skip to content
Shelf Cloud Shelf Cloud docs

What we verify before selling it

Objective

Section titled “Objective”

Most of what a cloud tells you about itself is a claim. Some of what this one tells you is checked by a machine, and the deployment refuses to proceed if the check fails.

This page says which claims those are, so you know which ones are load-bearing.

1. The hardware is at least as big as the catalog sells

Section titled “1. The hardware is at least as big as the catalog sells”

Before the platform serves, it measures the machine it is running on and compares it with what the catalog offers:

ResourceRule
CPUReal threads × the declared overcommit ceiling must cover the advertised vCPU
MemoryPhysical memory must cover the advertised memory. Never overcommitted
StorageFree pool space plus what has already been sold must cover the advertised capacity

If any of the three falls short the deploy fails, with a message naming the resource, the real figure and the catalog figure.

The consequence for you: the capacity figures on Instance types are not aspirational. The platform will not run on hardware that cannot honour them.

Memory is the one with no give in it. CPU may be oversubscribed up to the ceiling the catalog itself declares; memory never is, so a shape promising 8 GB has 8 GB of real memory behind it.

2. Every AWS alias tells the truth about size

Section titled “2. Every AWS alias tells the truth about size”

Our shapes carry AWS instance-type names as aliases, so existing tooling works unchanged — m5.large resolves to a shape of ours.

That claim is verified, not asserted. On every deploy, each alias is checked against a public feed of real AWS instance specifications:

  • An alias unknown to AWS fails the deploy.
  • An alias whose vCPU or memory differs from the shape it points at fails the deploy, with a message naming both sides — “x is 4c/16384MiB on AWS but 2c/8192MiB in cd-…”.

The spec feed is refreshed daily and is the same data the pricing rule uses, so the size an alias promises and the price derived from it cannot drift apart.

[!primary]

An alias is never a lie about size. That is why shapes with no honest AWS equivalent carry no alias at all rather than a near-enough one — the 1-vCPU shapes have none, because no current-generation, non-burstable AWS type is that small.

What this buys you: instance_type = "m5.large" in a module written for AWS gets exactly the vCPU and memory m5.large means. It does not get “roughly that”.

3. No set of allocations can oversell the box

Section titled “3. No set of allocations can oversell the box”

Every tenancy ceiling is declared, and the first thing the process that creates them does is add them all up and assert the total fits inside what the catalog says the hardware sells.

Adding a tenancy, or raising an existing one, past that line fails before anything is touched — no partial application, no first-come-first-served race discovered later under load.

The fix is never to raise the ceiling. It is to shrink another allocation, or to free capacity.

See Quotas and limits.

What these checks do not cover

Section titled “What these checks do not cover”

Stated so the guarantees are not read as broader than they are:

  • Not availability. Nothing here promises the machine stays up. One box, no redundancy, no failover.
  • Not performance under contention. The volume IOPS figure is published and divided honestly, but it is not yet enforced per volume — see Volume types.
  • Not durability. No backups, no mirroring across disks, no cross-host replication.
  • Not price stability over time. Prices are recomputed from a published rule; the rule is fixed, the numbers move with the market.
  • Not that everything on offer is priced. A shape with no rating mapping is launchable and unbilled — a defect, not an offer.

Why publish this

Section titled “Why publish this”

Because the interesting question about any cloud’s specification is not what it says, but which parts of it something would notice if they became untrue.

Here, three things would: the hardware being smaller than the catalog, an alias lying about size, and allocations summing past capacity. Everything else on this platform is a claim you are trusting us on, and the pages describing it try to say so plainly.

Go further

Section titled “Go further”