Lago

Lago is an open-source billing and metering platform that lets companies build usage-based, subscription, and hybrid pricing models without building a homegrown billing stack from scratch. Founded in 2021 by two early Qonto employees, it offers a free, self-hostable core plus managed cloud tiers, and is used by companies such as Mistral AI, PayPal, Groq and Synthesia to meter events and issue invoices at scale.