Lago

Lago is the leading open-source billing engine designed to handle the complexity of usage-based and hybrid billing models that traditional SaaS billing tools struggle to support. Architected as an API-first solution, Lago decouples the billing logic from the payment gateway, allowing engineering teams to implement sophisticated metering, rating, and invoicing workflows without vendor lock-in. By 2026, Lago has positioned itself as the industry standard for AI and infrastructure companies that require high-throughput event processing (metering) to bill users based on tokens, compute time, or API calls. Its technical stack utilizes a robust event-driven architecture, typically deployed via Docker, leveraging PostgreSQL for persistence and Redis for high-speed event ingestion. The platform provides a bridge between complex usage data and financial compliance, offering automated tax calculation, multi-currency support, and seamless synchronization with ERP systems. It is the preferred choice for Lead AI Architects looking to build scalable monetization layers while maintaining full sovereignty over their financial data and avoiding the 'Stripe tax' on high-volume transactions.