Hi everyone, We built Invariant.dev to solve a specific problem we kept running into: silent failures in asynchronous event pipelines. If you work with event-driven architectures or background queues, you probably know the pain. Traditional monitoring tools are great at catching crashes and 500 errors, but they are completely blind when a step in a business flow simply *never* happens—like a user who signs up but never gets their onboarding email, or an order that gets stuck before shipping. To solve this, we wanted a simple way to track time windows between events without writing complex state tracking logic or custom cron jobs. With Invariant, you can: 1. **Define rules** between events (e.g., `ORDER_CREATED` must be followed by `ORDER_SHIPPED` within 2 hours). 2. **Stream event states** via a simple REST API or cURL. 3. **Receive alerts** on Slack or via Webhooks the millisecond a window is breached. We have a free tier that covers small workloads (up to 10 rules and 100k events/month), and a Pro plan for $5/month if you need to scale. We'd love to know how you currently monitor these kinds of silent failures, and we are open to any feedback or questions you have. Thanks for reading!

Invariant.dev

Enforce business rules and event SLAs in real-time

Enforce business rules and event SLAs in real-time