Summary

  • EC2 Mac bills for a Dedicated Host with a minimum allocation of 24 hours. Per-second metering does not make the minimum purchase a second, or release the host when a build finishes.
  • Stopping or terminating an instance triggers a scrub during which billing pauses and the host cannot run the next instance. A smaller bill can coexist with a longer wait for the next release.

A compiler can finish its work long before procurement has finished explaining the purchase. EC2 Mac offers a particularly neat example: seconds on the meter, a day on the opening order. A short build can require a host allocation whose minimum duration is 24 hours.

The Amazon EC2 FAQ states both per-second billing and the 24-hour minimum Dedicated Host allocation. AWS attributes the minimum to compliance with Apple’s macOS Software License Agreement. After the minimum, the customer can release the host without further commitment to its use.

The measurement is fine-grained; the minimum order is not. Making a compiler faster improves the work performed inside that order. It does not, by itself, shrink the order. A dashboard that reports successful build minutes can therefore tell a perfectly accurate story about the wrong unit of purchase.

There is a whole machine behind the button

The EC2 Mac documentation identifies the Dedicated Host as the billing unit. Its instance carries no additional instance charge. Each host supports one Mac instance, on bare metal, for work such as developing, building, testing and signing applications for Apple platforms.

That is a useful way to bring a Mac environment into a cloud workflow. It is still a purchase of machine capacity, rather than a charge attached only to the minutes that produced a successful application build. Finishing the work and ending the allocation are separate events.

A host can be shared among accounts or organisational units within the same AWS organisation. Sharing broadens access; it does not manufacture extra Mac instances on that host. Someone still has to decide which jobs can use the environment and how their demands fit together.

The Dedicated Hosts pricing page explicitly gives EC2 Mac a minimum host allocation and billing duration of 24 hours. The generic 60-second minimum shown for other hosts is no use in this calculation. Stopping an instance, terminating it and releasing the host are distinct actions. A successful exit code does not press all three buttons.

This matters to internal accounting. One job causes a new allocation; another occupies capacity that has already been acquired. They can have identical execution times and very different effects on the next purchase. Dividing all expenditure by completed build minutes conceals the decision that made the capacity order larger.

The free interval still occupies the calendar

The less familiar part of this arrangement is a pause that AWS does not charge for. Treating every unavailable minute as a paid minute would miss it.

The Mac stop and termination instructions describe the scrub triggered by either operation. It erases the internal SSD, clears persistent NVRAM variables and updates firmware. While the host is pending, metering and billing pause. The scrub duration is unbilled.

The stopped instance cannot restart during that period, and a new instance cannot launch on the same host. The customer waits for scrubbing to finish and the host to become available. An empty patch on the invoice remains an occupied patch in the delivery schedule.

AWS documents scrub durations of up to 50 minutes for x86 Macs, or up to three hours when a firmware update is needed. For Apple silicon Macs, the process can take up to 4.5 hours. These are possible durations, not measured averages or a fixed delay attached to every job. They are enough to make an immediate handover an unsafe scheduling assumption.

The scrub performs real work between uses. Changing a project name does not erase the previous machine state. A sensible purchasing model accommodates the required changeover rather than pretending it can disappear to make utilisation look better.

The sources do not provide a worked invoice combining a particular scrub interval with the 24-hour minimum; that calculation needs the actual state history and bill. Automatically subtracting 4.5 hours from the minimum would invent a rule. Charging for the scrub in an example would invent another. Allocated time, billable time and time available for work deserve separate columns.

Readiness is a different product

Preparation also comes before the build. With AWS-provided images, the documentation gives approximately six to twenty minutes until an instance is ready for connection. EBS size, startup scripts and software in custom images can extend that interval. A compiler log that begins after preparation measures the middle of the journey.

Combining compatible jobs within an existing allocation can reduce the need to open another one. Keeping an environment ready can also have value when the next release needs an immediate start. These are choices about the service being purchased, not simply the speed of the processor.

A low-cost place in a queue and a machine ready on demand make different promises. They may produce the same final file at different times. Filling every available slot is not proof of good purchasing if an urgent job then has no ready capacity. Nor do incompatible environments or isolation requirements become compatible because a utilisation chart would prefer them to share.

EC2 Mac is offered On-Demand, not through Spot or Reserved Instances. Savings Plans can reduce spending. A discount changes the price; it does not make a host available while scrubbing continues. The calendar does not inherit every saving on the invoice.

Actual job arrivals, occupancy, applicable prices and the cost of waiting would determine when a particular team should retain or release capacity. Without those inputs, there is no universal answer. There is, however, a useful purchasing question: is the company buying execution when a slot opens, or the ability to begin when its product team asks?

Faster builds remain worth having. They simply cannot stand in for a whole purchase that includes a minimum allocation, preparation and changeover. The meter may count seconds impeccably. Someone still has to account for the day on the order.