A full time employment relationship does not have that shape. That mismatch is the decision.
When full time is right
You can name the next three deployments. Several locations, several products, a roadmap of integrations that will not run out.
The knowledge has to compound internally. Each deployment teaches something about your business that the next one uses.
You can absorb the between times. There will be gaps between projects. If those gaps are filled with useful work, full time is efficient. If they are filled with looking for work, it is not.
When fractional is right
One or two deployments in view. You have a specific thing that does not work, and you do not know whether there will be a third.
You need to start now. Hiring for this profile in this market commonly takes about three months. A stalled rollout does not wait a quarter.
You are unsure of the shape. A fractional engagement is a cheap way to learn what the role should be before committing to a salary.
The real comparison
Not monthly cost. Cost per deployment completed and handed over.
A full time engineer between projects is expensive in a way that never appears on an invoice. A fractional engineer who never hands over is expensive in a way that appears every month, forever.
The clause that decides whether fractional works
Make the handover a deliverable with a date, not a promise at the end:
- A runbook that an internal person has followed successfully, not just received
- Credentials and access that survive the engagement ending
- A named internal owner from week one, who participates rather than waits
- Documentation written during the build, not compiled afterwards
If a provider is uncomfortable with that clause, you have learned something early and cheaply.
The hybrid that works in practice
Fractional engineer builds and documents. Internal person owns and operates, shadowing during the build rather than receiving at the end.
Knowledge transfers by participation. A handover meeting transfers a document and very little else.
The question to ask either way
What will exist when this ends, and who runs it?
Anyone whose answer is a support retainer is offering you a dependency. That can be a reasonable purchase, but you should price it as one rather than discover it later.