Lago

Lago is an open-source metering and usage-based billing platform that enables SaaS, AI, fintech, and API companies to implement complex consumption-based pricing models — providing the infrastructure for tracking usage events, aggregating them into billing metrics, managing subscription plans, generating invoices, and integrating with payment processors and accounting systems. Founded in 2021 in Paris and a Y Combinator graduate, Lago raised $22 million from investors and serves customers including Mistral.ai, Together.ai, and Juni with both a free self-hosted version and a paid cloud SaaS offering.\n\nLago's platform addresses the engineering complexity of usage-based billing — which requires reliable high-volume event ingestion (every API call, compute minute, or message sent), real-time aggregation into billable metrics (sum of API calls, maximum storage, seat counts), and invoice generation that correctly maps complex pricing tiers, overages, and credits. Building this infrastructure in-house typically takes multiple engineering months and ongoing maintenance; Lago provides it as open-source infrastructure that companies can deploy and customize.\n\nIn 2025, Lago competes in the billing infrastructure and monetization platform market with Stripe Billing, Chargebee, Recurly, and Zuora for subscription and usage billing systems. The shift toward consumption-based pricing (pay per API call, per compute unit, per message) has accelerated with the growth of AI and infrastructure companies that naturally charge per usage rather than per seat. Traditional subscription billing platforms (Chargebee, Recurly) were designed for fixed subscription billing and have added usage billing as an afterthought — Lago's usage-first architecture is better suited for the complex consumption models modern AI and API companies need. The open-source approach builds community trust and allows customization that proprietary platforms don't permit. The 2025 strategy focuses on growing enterprise cloud customers and deepening the platform's AI company billing capabilities.