FA-59812 / Subscription proration billing / Member archive

Package pricing with milli-unit usage: unit rounding grain · case 02

Customers with many small events are billed for far more units than they used.

Member previewVariant 2 · 3 implementations · 8 checks per implementation

Case contract

Input {events in milli-units, free units, div (units per package), round up|down, price per package}. Units = ceil(sum(events)/1000) once per invoice. Billable = max(0, units - free). Packages = ceil or floor(billable/div) by round. Return [units, packages, packages*price].

Why this case matters

Package pricing rounds usage twice, and doing either rounding at the wrong grain changes the bill.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression 0	`[10, 1, 250]`	`[9, 1, 250]`	Failed

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