Lago

In today's rapidly evolving software landscape, managing subscription and usage-based billing systems has become increasingly complex for tech companies. Lago has emerged as a transformative solution in this space, combining advanced technical capabilities with developer-friendly design principles. Through its innovative open-source and premium solutions, Lago addresses the billing challenges faced by growing companies while providing the flexibility required for modern software monetization. In this article, we explore Lago's technical architecture, core features, and market impact, highlighting how the company has become a leading force in the billing technology ecosystem.

Product Overview

Lago offers two main billing solutions: Lago Premium and Lago Open Source. Lago Premium, described as the optimal solution for teams requiring control and flexibility, includes advanced features such as instant charges, customer portal, spending minimums, email invoices, grace periods, time zones, credit notes and refunds. The platform supports both cloud and self-hosted options through comprehensive technical documentation and developer resources available via GitHub.

The company's open-source solution enables flexible deployment with customizable invoices and automatic tax management. It supports pay-as-you-go pricing models through real-time usage prepayment and recurring top-up rules. The system also features full plug-and-play metering functionality and connects directly to data sources without the need for pre-aggregation.

Lago's technical architecture operates on a real-time, event-based system that prevents duplicate events while providing the highest level of granularity in customer consumption information. The platform processes usage events through six aggregation types: COUNT, COUNT_UNIQUE, LATEST, MAX, SUM, and WEIGHTED SUM, allowing businesses to define how much customers should pay for using their services. The company's approach enables seamless integration across multiple categories including payments, accounting, taxes, CRM, and marketplaces through robust third-party integrations.

Core Features

Lago's core features enable businesses to create flexible pricing models while providing detailed usage tracking. The system supports multiple pricing configurations through its four aggregation types: COUNT, COUNT_UNIQUE, LATEST, and MAX, which help determine how much customers should be charged based on their usage patterns.

The company's billing solution includes customizable invoices, automatic tax management, and payment collection capabilities. Users can define different pricing tiers and apply coupons or discounts through modular functionality. The platform also supports add-ons and one-off invoices, allowing businesses to charge for additional services or features.

For businesses requiring more complex billing logic, Lago provides detailed configuration options. This includes setting spending minimums, enabling grace periods for adjusting usage after billing cycles, and managing time zone differences for global customers. The system processes payments through Stripe and supports multiple payment providers including GoCardless, Adyen, and Cashfree Payments.

To help integrate seamlessly with existing business systems, Lago offers native integrations with popular tools including NetSuite, Salesforce CRM, and AWS Marketplace. The platform also provides robust third-party integration capabilities through API access and reverse-ETL functionality with Segment.com and Hightouch. This allows businesses to sync customer data, track usage events, and automate billing processes.

Technical Architecture

Lago's technical architecture operates on a real-time, event-based system that processes usage events while preventing duplicates. The event system provides the highest level of granularity in customer consumption information, with each product feature requiring a specific event trigger, either through action or periodic sending.

The system aggregates events into billable metrics through six primary aggregation types: COUNT, COUNT_UNIQUE, LATEST, MAX, SUM, and WEIGHTED SUM. These aggregation types enable precise calculation of customer charges based on their usage patterns across different service tiers. The COUNT type simply counts the number of event occurrences, while COUNT_UNIQUE tracks distinct values of predefined properties. The LATEST type returns the most recent value for a specific property, useful for time-sensitive usage tracking.

The MAX type determines the highest value for a property during a billing period, appropriate for usage caps or limits. SUM calculates the total amount of a property across events, essential for flat-rate or fixed-quantity pricing models. WEIGHTED SUM provides more sophisticated billing logic by calculating sums based on time usage prorated across periods, ideal for services billed by consumption duration.

These aggregation methods enable Lago to support a wide range of pricing models, from simple usage-based billing to complex hybrid plans combining subscription and usage components. The platform's flexibility allows businesses to define exactly how much customers should pay for using their services, while the real-time event processing ensures accurate and timely billing information.

Market Position

Lago's innovative approach to billing has garnered significant attention from the software development community. The company's open-source solution has become the #1 standard on GitHub in its category, demonstrating its appeal to developers and billing engineers.

The market has responded enthusiastically to Lago's platform-led strategy. The company serves leading tech companies including Mistral (AI, $640M raised at $6 billion valuation), Accel-backed Swan (Embedded banking), Together.ai ($102.5M raised at $1.25 billion valuation), and Groq ($300M raised at $2.5 billion valuation). These high-profile customers represent a diverse array of industries, from artificial intelligence to DevTools and fintech, highlighting Lago's broad market appeal.

The company's success is built on a strong foundation of engineering expertise. Lago emerged from Qonto.com, where its founders led revenue growth from pre-product to Series D, building and scaling the monetization system that took Qonto from zero to $100M+ in revenue. This experience directly informed Lago's approach, which was initially met with skepticism from Romain at Qonto, who famously declared he "would NEVER touch a billing system again." The team's technical background allows them to address the billing nightmares that typically plague growing companies, such as delayed launches, billing errors, and churned users.

Financially, Lago has raised $22 million in funding through Y Combinator, FirstMark Capital, SignalFire, and other notable investors including Meghan Gill (formerly of MongoDB) and Clément Delangue (CEO of AI open platform Hugging Face). The company's financial backing and strategic investor base provide a solid foundation for continued growth.

The current team, composed of 1,000+ billing engineers and product managers, brings a unique perspective to the billing market. As Raffi explained to Romain at Qonto, their approach focuses on building rather than billing, allowing developers to eliminate the headache of managing billing systems. This engineer-friendly approach is reflected in Lago's technical architecture, which provides the transparency and control developers need while handling the complex calculations required for modern billing systems.

Company Background

The company's origins stem from Qonto's history of underestimating the engineering nightmare billing would create, learning the hard way about delayed launches, billing errors, and resulting churned users. When Raffi initially pitched the idea of Lago to Romain, a senior billing engineer at Qonto, he was met with resistance - Romain famously declared he would "NEVER touch a billing system again." However, Raffi managed to convince Romain to join the team, channeling his experience to prevent future billing nightmares.

At Qonto, the team led revenue growth from pre-product to Series D, building and scaling the monetization system that took the company from 0 to $100M+ in revenue. This experience directly informed Lago's approach, which was initially met with skepticism from Romain. The team's technical background allows them to address the billing nightmares that typically plague growing companies, such as delayed launches, billing errors, and churned users.

The founders drew from a proven track record of building complex revenue systems. At Qonto, they navigated the challenges of a growing "billing engineering" team that was both expensive and hard to retain, learning firsthand that their "pricing strategy" nearly shifted to "what's the easiest option to implement" rather than "what's the best for the company."

The technical foundation of Lago emerged from this challenging experience, focusing on creating a system that could handle the complexities of modern revenue growth. The company's approach is based on an open-source and "platform" model, enabling businesses to build flexible and scalable monetization systems without the typical engineering hurdles. This platform-led strategy has proven successful, with Lago becoming the #1 standard on GitHub in its category, serving companies including Mistral, Accel-backed Swan, Together.ai, and Groq.