Lago — Open Source Usage-Based Billing API

What it is

Lago is an open-source billing API designed for usage-based pricing models. It handles event ingestion, metering, subscription management, invoice generation, and payment orchestration. The project is licensed under AGPL-3.0.

Lago targets SaaS companies, API platforms, and AI services that charge based on consumption -- API calls, tokens, compute hours, or storage. It replaces proprietary billing platforms like Stripe Billing, Chargebee, or Zuora for teams that need full control over their billing logic.

How it saves time or tokens

Lago provides a complete billing pipeline out of the box. Instead of building metering, aggregation, proration, and invoice rendering from scratch, you configure billing plans and meters through the dashboard or API. Events are ingested via a simple HTTP endpoint, and Lago handles the rest.

The self-hosted deployment means you avoid per-transaction fees from managed billing platforms, which matters at scale for high-volume usage-based models.

How to use

1. Clone the repository and start with Docker Compose: git clone https://github.com/getlago/lago.git && cd lago && docker compose up -d.
2. Open the dashboard at http://localhost:80 and configure your billing plans, meters, and pricing tiers.
3. Ingest usage events from your application via the REST API and let Lago generate invoices automatically.

Example

# Start Lago
git clone https://github.com/getlago/lago.git
cd lago
docker compose up -d

# Ingest a usage event
curl -X POST http://localhost:3000/api/v1/events \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -H 'Content-Type: application/json' \
  -d '{
    "event": {
      "transaction_id": "txn_001",
      "external_customer_id": "customer_123",
      "code": "api_calls",
      "timestamp": 1700000000,
      "properties": {"tokens": 1500}
    }
  }'

Related on TokRepo

• API tools -- Tools for building and managing APIs
• Self-hosted tools -- Self-hostable infrastructure for development teams

Common pitfalls

• Lago uses AGPL-3.0 licensing. If you modify the source and serve it as a SaaS, you must open-source your changes. Review the license before deploying in proprietary environments.
• The Docker Compose setup requires PostgreSQL and Redis. Ensure both services have adequate resources for production workloads with high event volumes.
• Invoice PDF generation depends on a separate service. If you need custom invoice templates, you must configure the PDF rendering component separately.