Multitenant instances on AWS statically partition the hardware (CPU, RAM, network), so tenants don't really share all that much. Memory bandwidth is probably the only really affected resource.
> Second, they don’t constrain random usage enough.
AWS now has billing alerts with per-hour resolution and automatic anomaly detection. There are third-party tools that do the same.
You are missing several points:
First, density. Cloud providers have huge machines that can run lots of VMs, and AWS in particular uses hardware (”Nitro”) for hypervisor functionality so they have very low overhead.
Cloud providers also don’t do “hardware” partitioning for many instance types. AWS sells “VCPUs” as the capacity unit; this is not necessarily a core, it may be time on a core.
Cloud providers can also over-provision; like airlines can sell more seats than exist on a plane, cloud providers can sell more VCPUs than cores on a machine, assuming (correctly) that the vast majority of instances will be idle most of the time, and they can manage noisy neighbors via live migration.
And lots of other more esoteric stuff.
But they don't. AWS overprovisions only on T-type instances (T3,T4,T5). The rest of the instance types don't share cores or memory between tenants.
I know, I worked with the actual AWS hardware at Amazon :) AWS engineers have always been pretty paranoid about security, so they limit the hardware sharing between tenants as much as possible. For example, AWS had been strictly limiting hyperthreading and cache sharing even before the SPECTRE/Meltdown.
AWS doesn't actually charge any premium for the bare metal instance types (the ones with ".metal" in the name). They just cost a lot because they are usually subdivided into many individual VMs.
For example, c6g.metal is $2.1760 per hour, and c6g.16xlarge is the same $2.1760. c6g.4xlarge is $0.5440
> And lots of other more esoteric stuff.
Not really. They had some plans for more esoteric stuff, but anything more complicated than EC2 Spot does not really have a market demand.
Customers prefer stability. EC2 and other foundational services like EBS and VPC are carefully designed to stay stable if the AWS control plane malfunctions ("static stability").
If you turn on a .metal instance, your account will be billed (at least) $2/hr for the privilege for every region in which you do so. A fact I didn't know until I had racked up more charges than expected. So many junk fees hiding behind every checkbox on the platform.