How Inngest works

Inngest allows you to serve durable workflows via HTTP in your own infrastructure, without managing event streams, orchestration, or state. In this section, we'll detail how this is possible, including:

• Function configuration and deployment
• The execution model, and how functions are invoked
• How function state is managed
• Function Versioning
• Limitations

We'll walk through these in order, introducing how Inngest works end-to-end.

Function configuration and deployment

Prior to execution, functions must be configured served, and registered. Functions are configured via your language's SDK. There are two key parts to function configurations: the definition and the triggers. For example:

inngest.createFunction(
  // Function definition
  {
    id: "post-registration",
    concurrency: 50,
    idempotency: "event.dat.auser_id",
  }
  // The triggers.
  { event: "api/user.created" },
  async ({ event, step }) => {
   // Your own durable workflow here.
  },
);

In this example, the function is defined with an ID, a concurrency limit, and an idempotency key (for exactly-once processing over 24 hours). It also specifies its trigger: this function runs every time the api/user.created event is received.

Functions are configured then served via your own API, on your own infrastructure, via our serve handlers. Once served, you must deploy your functions to Inngest.

Function deploys

In order for Inngest to execute your functions, Inngest must know where your functions are hosted. This happens via deploys. There are several things to consider:

1. Functions are served on your own infrastructure, via your own deploy process
2. We support both servers and serverless functions
3. Inngest is typically unaware of when your deploys occur.

The deploy process is a simple handshake between the SDK and Inngest. The SDK reaches out to Inngest with a secret key (signing key), and pushes function configuration to a registration endpoint. For more information, read the deploys guide.

Function invocation

As part of the deploy process, Inngest sets up new listeners for your environment's event stream.

Function execution

The execution model

Function state