Stepkit, an Open and Cross-Platform Durable Execution Standard

Hi HN! I’m Tony, one of the co-founders of Inngest (https://inngest.com/). Wanted to show you something we’re working on: StepKit.

StepKit is an open source SDK and framework for building and iterating on durable workflows that run on any platform (self-hosted, Inngest, Cloudflare, Netlify, etc.) without requiring any provider or bundler-specific code.

Here’s the repo: https://github.com/inngest/stepkit.

StepKit extracts the core execution loop that we built in Inngest and makes it fully open, Apache 2, and hackable/pluggable to different backends. We don’t want people to have to go through multiple major versions in SDKs to learn the lessons we’ve already learned in production:

It needs to work anywhere: This SDK is push-based and receives tasks via API endpoints, so it works anywhere (servers, serverless, k8s, etc). That's also customizable. It doesn’t need any specific runtime or bundler support.

It needs to be complete: StepKit includes the entire execution engine: step discovery, memoization, a core event loop to turn async steps into generators without relying on `try/catch` based control, and middleware for extensibility (eg, end-to-end encryption, Sentry integrations, and so on).

It needs a simple API: StepKit APIs are explicit `step.*()` functions, which we designed in our original Inngest SDK back in 2022. They’re easy to read, understand, implement, and use. They contain all of the primitives for durable execution: steps, suspend/resume, human-in-the-loop, and observability. These same APIs have also been adopted by Cloudflare, Netlify, Convex, and others, and support billions of runs every month.

It needs to be resilient: Steps tolerate changes when refactoring, and provide the building blocks of durable execution without complex abstractions.

We’re starting with in-memory, filesystem, Inngest, and Cloudflare (WIP) drivers, with more coming soon.

The roadmap includes middleware, compatible SDKs in different languages, as well as extensions like concurrency controls and idempotency: https://github.com/inngest/stepkit/discussions/52.

Excited to see what you think!