Fractional works when the work has a finish line and nobody is blocked waiting on it. It fails, quietly, when the work has a roadmap attached — because half the hours is not half the output, and the difference shows up as latency rather than as a line on an invoice. The rough boundary: under about ten hours a week of a specialist, buy fractional; over about twenty-five hours a week of delivery, buy dedicated and stop optimizing the hourly rate.
What does "fractional" actually mean when you buy it?
Three products get sold under one word, and confusing them is how most of these engagements go wrong.
- Fractional leadership. A CTO, principal or architect for a few hours a week — five to ten is the range usually advertised. You are buying decisions and direction, not throughput.
- A part-time individual contributor. A working engineer at part-time hours — fifteen to twenty-five a week is the range usually advertised, on your backlog. This is the one that usually disappoints.
- A shared seat. A vendor sells "half an engineer" who is also on two other accounts this month. It is marketed as part-time and it is actually contended. Ask how many other clients that person has in the next thirty days, and expect a number, not a philosophy.
When is fractional genuinely the right call?
These are cases where a dedicated full-time seat is the wrong purchase, and saying otherwise would cost you money.
- Work with a defined end. A migration, a payments integration, a design system, an evidence push before a SOC 2 audit. The scope finishes, context does not need to compound, and no monthly commitment outlives the project.
- A scarce skill needed in doses. A security review before an enterprise deal, a quarterly look at the data model, a feasibility read that answers yes or no in three weeks. Forty hours of a real specialist beats 160 hours of someone learning the specialty on your clock.
- Before there is a team. Pre-product, one technical founder, no code base worth maintaining yet. Six hours a week of an architect keeping early decisions from becoming next year's rewrite beats an extra pair of hands.
- A surface in maintenance. A service that changes twice a quarter does not need a person, it needs a person who is reachable.
- You are buying a decision, not a deliverable. Vendor selection, an architecture call, build versus buy.
If you are on that list, fractional is the better buy. The rest of this is the other case.
Where does part-time quietly fail?
The failures do not announce themselves: nobody misses a deadline in week two, the engagement just runs slower than planned, for structural reasons rather than personal ones.
Context reload is close to fixed per session, not per hour. An engineer working Tuesday and Thursday pays the cost of getting back into the code base twice a week, out of a shorter day. Twenty hours across five days is worse than twenty across two, and both are worse per hour than forty across five.
Latency compounds in the blocking direction. If the engineer works Monday, Wednesday and Friday, a question raised Wednesday afternoon that needs your answer gets acted on Friday. Two exchanges cost a week; dedicated, they cost a day. This is the largest hidden cost of part-time, and it is invisible on the invoice because every billed hour was genuinely worked.
Nobody owns anything. Owning a service means being called when it misbehaves and approving changes to it. Neither survives three days of availability, so the work drifts back to your full-time people — the outcome you were hiring to avoid.
The overlap gets thin twice. Brazil is UTC−3 all year, one to two hours ahead of U.S. Eastern and four to five ahead of Pacific, with no daylight saving to soften the edges. That is a generous window for a full-time engineer and a fragile one for a part-time engineer whose fifteen hours may land on your planning days. Specify the hours and the days, never just the total; the overlap calculator shows what is actually shared with your zone.
The candidate pool is a different pool. Strong seniors tend to be engaged full-time. One genuinely available for twenty hours a week is running their own product, holding several clients, or between full-time engagements — and the third leaves when a full-time offer arrives, which is churn you did not budget for.
Is half an engineer half the price?
Run the arithmetic first, because the hourly number is what does the persuading. A dedicated senior at the published rate of $4,900 a month, across a 160-hour month, is about $31 an hour; a mid-level seat at $3,500 is about $22, a tech lead at $6,400 is $40. Those are flat, all-inclusive monthly numbers, so the effective hourly moves only if the hours do.
Fractional work is quoted hourly and at a premium, reasonably so, since the seller carries the gaps between engagements. Take the quote you actually receive and find where it stops being cheaper:
| If your fractional quote is | It matches a dedicated senior at | Roughly per week |
|---|---|---|
| $60 an hour | 82 hours a month | 20 hours |
| $80 an hour | 61 hours a month | 15 hours |
| $100 an hour | 49 hours a month | 12 hours |
| $125 an hour | 39 hours a month | 10 hours |
Those are breakeven points against one published rate, not a market survey — put your own quote in the first column. The pattern is the point: somewhere between ten and twenty hours a week, part-time starts costing more than full-time and delivering less of it. The cost calculator runs the same arithmetic across a mix of levels, and the budget piece covers the lines that sit outside the rate in either model.
One asymmetry the table cannot show: the dedicated number is fixed and the fractional one is not. Hourly engagements expand in busy months, when a finance surprise is least welcome.
The two questions that settle it
Does the work end? If there is a date after which nobody needs this person, fractional fits. If the honest answer is "there is a roadmap," it does not.
Is anyone waiting on this person? If yes — a reviewer, a dependent service, a release train — every non-working day of theirs is a stalled day of somebody else's. Part-time is cheap only when the queue behind it is empty.
Two yeses means fractional. One of each usually means you want a dedicated engineer one level down rather than a fractional one a level up — the trade most teams never consider.
The hybrid that beats both more often than people expect
One dedicated engineer who owns the surface, plus a few fractional specialist hours elsewhere for the skill you need occasionally. The dedicated seat carries continuity and ownership; the fractional hours cover the security review, the infrastructure call, the data model. Nobody pays full-time rates for a quarterly opinion, and nobody waits three days for a merge. It is rarely proposed, because most vendors sell one shape.
What belongs in the contract either way?
- Hours and days, not just hours. "Twenty hours a week" and "Monday, Wednesday, Thursday, 9 AM to 3 PM Eastern" are different agreements, and only one can be planned against.
- A written response commitment. One business day is a reasonable bar. Without it, part-time becomes whenever.
- Exclusivity, or an honest count. Either the person is yours during those hours or not. Both are workable. Not knowing is not.
- Notice in both directions. Thirty days either way is what we write, and a reasonable thing to ask for. An exit clause only one side can use tells you how the rest was written.
- IP assignment naming the entity doing the work. The clause that breaks when work is contracted through individuals abroad; the mistakes guide covers what surfaces after signing.
Where we sit, and where we are the wrong answer
HireBrazilDevs places dedicated, full-time engineers. That is the only shape we sell: a flat monthly rate, month to month, thirty days notice either way, free replacement inside the first thirty days. If what you need is six hours a week of an architect, or a bounded migration with a date on it, we are not the right purchase — and hearing that early beats a proposal bent to fit.
Where it does fit, the case for dedicated is not loyalty or throughput mysticism. It is that the queue behind the engineer is never empty, and part-time is only cheap when it is.