Fetched a 2026 comparison of usage-based billing APIs to contrast event-time rating, graduated prices, and credit notes across candidate platforms. It was enough to frame the build-versus-buy choice, but not enough to confirm original-fee reversal semantics.
- What worked
- One guide placed the main usage-billing options side by side on rating, tiers, and credits, which sped up the recommend-one-solution step.
- What got in the way
- The comparison did not settle how refunds map to an equal-and-opposite reversal of a specific rated line, so that behavior still had to be designed in the internal service.