If your product charges customers based on how much they actually use — API calls, compute minutes, tokens, seats-per-day — you need a billing system built for metered pricing, not a bolt-on to a flat-subscription tool. Two names keep coming up in our catalog when SaaS and AI companies compare usage-based billing platforms: Metronome, the enterprise-grade engine now owned by Stripe, and Lago, the open-source alternative you can self-host for free. Here's how they actually differ.
Metronome: the enterprise pick
Metronome tracks and prices metered usage in real time, and counts OpenAI, HubSpot, Cribl, Astronomer, and Fly.io among its reference customers. Stripe acquired it in January 2026, which brings credibility and a likely path to tighter native Stripe integration — but also uncertainty about its long-term roadmap and pricing under new ownership.
Price: Starter tier includes $100,000 of billable volume then 0.8% beyond that, plus 10M included metering events then $0.04 per 1,000 events. Custom tier is quote-based with advanced integrations and stronger SLAs.
Strengths: pricing changes deploy in under an hour without engineering resources; cohort-based pricing experiments; proven at large scale with major AI companies as references.
Limits: the 0.8% overage fee adds up fast at scale; Custom-tier pricing isn't published; and the recent acquisition means roadmap and pricing could shift under Stripe.
Lago: the open-source pick
Lago is open-source metering and usage-based billing infrastructure you can self-host for free, or run on their managed cloud. It's less battle-tested at large scale than Metronome, but it costs nothing to start and doesn't lock you into a vendor.
Price: Free to self-host (AGPL-3.0, Docker); cloud/hosted pricing isn't publicly specified.
Strengths: real-time billing, flexible pricing models, fully open source so you can audit or modify it yourself.
Limits: much less brand recognition and fewer public reference customers than Metronome, and cloud pricing isn't clearly published if you don't want to self-host.
Side by side
| Metronome | Lago | |
|---|---|---|
| Model | Managed SaaS, usage-based fees | Open source, self-host or cloud |
| Starting cost | $100K volume included, then 0.8% | Free (self-hosted) |
| Reference customers | OpenAI, HubSpot, Cribl, Astronomer, Fly.io | Not disclosed |
| Ownership | Acquired by Stripe (Jan 2026) | Independent, open source |
| Best fit | Large-scale AI/SaaS with complex metering | Startups wanting control and zero licensing cost |
Verdict
Pick Metronome if you're already billing at real scale, need proven reliability with reference customers like OpenAI, and don't mind paying a percentage of volume for a fully managed system now backed by Stripe.
Pick Lago if you want to avoid vendor lock-in, have the engineering capacity to self-host, or are early-stage and don't want a percentage-of-revenue billing line item yet.
Both solve the same underlying problem — metering usage and turning it into accurate invoices — the real difference is whether you'd rather pay for a managed, Stripe-backed platform or run the infrastructure yourself for free. For a broader look at the category, see our usage-based billing platforms guide.