Annual contract value is what a customer pays per year. It matters to an engineer because it sets the economics of the whole engagement: an enterprise deal large enough to absorb a dedicated engineer’s cost is why forward-deployed roles exist at all, and it is the denominator behind “is this deployment worth another month?”.
Worked example: a vendor with a seven-figure ACV can justify an FDE spending a quarter on one customer, because the renewal it protects dwarfs the salary; the same effort against a $40k contract is a loss the company cannot repeat. Gotcha: ACV is not profit — deployment-heavy revenue carries much lower gross margin, which is precisely the trade being made when a software company hires FDEs.