Start by creating a new Express project.

Enter the newly made directory:

Initialize the project:

Install workflow, express, nitro, and rollup

If using TypeScript, you need to install the @types/express package.

Configure Nitro

Create a new file nitro.config.ts for your Nitro configuration with module workflow/nitro. This enables usage of the "use workflow" and "use step" directives.

import { defineNitroConfig } from "nitro/config";

export default defineNitroConfig({
  modules: ["workflow/nitro"],
  vercel: { entryFormat: "node" },
  routes: {
    "/**": { handler: "./src/index.ts", format: "node" },
  },
});

Update package.json

To use the Nitro builder, update your package.json to include the following scripts:

{
  // ...
  "scripts": {
    "dev": "nitro dev",
    "build": "nitro build"
  },
  // ...
}

Create a new file for our first workflow:

import { sleep } from "workflow";

export async function handleUserSignup(email: string) {
  "use workflow"; 

  const user = await createUser(email);
  await sendWelcomeEmail(user);

  await sleep("5s"); // Pause for 5s - doesn't consume any resources
  await sendOnboardingEmail(user);

  return { userId: user.id, status: "onboarded" };
}

We'll fill in those functions next, but let's take a look at this code:

• We define a workflow function with the directive "use workflow". Think of the workflow function as the orchestrator of individual steps.
• The Workflow SDK's sleep function allows us to suspend execution of the workflow without using up any resources. A sleep can be a few seconds, hours, days, or even months long.

Let's now define those missing functions.

import { FatalError } from "workflow";

// Our workflow function defined earlier

async function createUser(email: string) {
  "use step"; 

  console.log(`Creating user with email: ${email}`);

  // Full Node.js access - database calls, APIs, etc.
  return { id: crypto.randomUUID(), email };
}

async function sendWelcomeEmail(user: { id: string; email: string }) {
  "use step"; 

  console.log(`Sending welcome email to user: ${user.id}`);

  if (Math.random() < 0.3) {
    // By default, steps will be retried for unhandled errors
    throw new Error("Retryable!");
  }
}

async function sendOnboardingEmail(user: { id: string; email: string }) {
  "use step"; 

  if (!user.email.includes("@")) {
    // To skip retrying, throw a FatalError instead
    throw new FatalError("Invalid Email");
  }

  console.log(`Sending onboarding email to user: ${user.id}`);
}

Taking a look at this code:

• Business logic lives inside steps. When a step is invoked inside a workflow, it gets enqueued to run on a separate request while the workflow is suspended, just like sleep.
• If a step throws an error, like in sendWelcomeEmail, the step will automatically be retried until it succeeds (or hits the step's max retry count).
• Steps can throw a FatalError if an error is intentional and should not be retried.

To invoke your new workflow, we'll create both the Express app and a new API route handler at src/index.ts with the following code:

import express from "express";
import { start } from "workflow/api";
import { handleUserSignup } from "../workflows/user-signup.js";

const app = express();
app.use(express.json());

app.post("/api/signup", async (req, res) => {
  const { email } = req.body;
  await start(handleUserSignup, [email]);
  return res.json({ message: "User signup workflow started" });
});

export default app;

This route handler creates a POST request endpoint at /api/signup that will trigger your workflow.

To start your development server, run the following command in your terminal in the Express root directory:

Once your development server is running, you can trigger your workflow by running this command in the terminal:

curl -X POST --json '{"email":"hello@example.com"}' http://localhost:3000/api/signup

Check the Express development server logs to see your workflow execute as well as the steps that are being processed.

Additionally, you can use the Workflow SDK CLI or Web UI to inspect your workflow runs and steps in detail.

# Open the observability Web UI
npx workflow web
# or if you prefer a terminal interface, use the CLI inspect command
npx workflow inspect runs

Enable Fluid compute before deploying. Workflow is designed to take advantage of Fluid compute for efficient suspension and resumption. Without Fluid compute enabled, each workflow resume incurs a separate function cold start, which can result in significantly higher costs.