Funes

A frictionless event sourcing experience for Rails developers.

Funes is designed to give RoR developers a frictionless experience building systems where history is as important as the present. Built with the one-person framework philosophy in mind, it honors the Rails doctrine by providing deep conceptual compression over what is usually a complex architectural pattern.

At its core is a declarative DSL that favors the interpretation of events over all the plumbing. Instead of wiring up event stores, replay loops, and serializers, you describe how each event affects state — and Funes handles persistence, ordering, concurrency, and materialization for you:

interpretation_for Debt::PaymentReceived do |state, event, _at|
  state.outstanding_balance -= event.principal_amount
  state.last_payment_at = event.at
  state
end

By distilling the mechanics of event sourcing into just three core concepts — Events, Streams, and Projections — Funes handles the underlying complexity of persistence and state reconstruction for you. It feels like the Rails you already know, giving you the power of a permanent source of truth with the same ease of use as a standard ActiveRecord model.

Unlike traditional event sourcing frameworks that require a total shift in how you build, Funes is designed for progressive adoption. It coexists seamlessly with your existing ActiveRecord models and standard controllers. You can use Funes for a single mission-critical feature while keeping the rest of your app in plain Rails.

Why event sourcing?

In a typical Rails app, data has no past — only a present. You update! a record and the previous value is gone. Event sourcing takes a different approach: store what happened as immutable events, then derive the current state by replaying them.

This gives you:

Complete audit trail — every state change is recorded, forever
Temporal queries — “what was the entity state on December 1st?”
Multiple read models — the same events, different projections for different use cases
Safer refactoring — rebuild any projection from the event log

It’s the right choice for any application where “what was true then?” matters as much as “what is true now?”