2.2k stars · Apache-2.0 · v1.0.0-beta.232 (2026-08-04)
Real-time usage metering with entitlements and balances — built for products whose unit of cost is a model call.
▶Repo detailsthe review · specs · pros & cons · install
What it is
A real-time usage metering service aimed at AI, API and infrastructure products: it collects usage events, aggregates them continuously, and enforces entitlements and balances. It sits between your application and whatever eventually bills the customer.
Why it matters
Grasppy's marginal cost is a model call, so the moment you offer a free tier you must answer "has this account used up its allowance?" on every single request — cheaply, without scanning a table. That is what an entitlement is, and it is the piece people hand-roll badly and then discover is wrong at the worst moment. OpenMeter is also the cleanest way to put a live "62 of 100 maps used" bar into the product, which is a retention and upgrade prompt as much as an accounting detail. It overlaps Lago (#1) directly: OpenMeter meters and gates, Lago meters and invoices. Read both and pick one — two counters that disagree is worse than neither.
- Built for token- and request-shaped usage, including entitlements and balances, not just end-of-month invoicing.
- Apache-2.0, so it can live inside a paid feature — unlike Lago's AGPL.
- Active and small: beta.232 on 4 August, with releases most months this year.
- Still
1.0.0-betaafter 232 tags — the project is not yet promising API stability. - The production deployment wants ClickHouse and Kafka; the light footprint is the development one.
- 2.2k stars and a young company behind it. This is a bet on a vendor as much as a dependency.
The remaining balance reads straight into the React header; the totals feed Lago or Polar for the actual charge.
A FastAPI dependency that checks the entitlement before an import starts and posts the usage event when it finishes.
