Inngest Function Handler Skill

Inngest Function Handler Skill

This skill defines the standards for building durable, multi-step workflows using Inngest.

🚨 HARD RULES (Strictly Follow)

1. NO setTimeout / setInterval:

   • ❌ Bad: await new Promise(r => setTimeout(r, 1000))
   • ✅ Good: await step.sleep("wait-1s", "1s")
   • Reason: Serverless functions time out; Inngest sleeps persist for up to a year.

2. NO Side Effects Outside Steps:

   • Any database write, API call, or non-deterministic logic (random, date) MUST be wrapped in step.run().
   • Reason: Inngest functions execute multiple times (memoization). Code outside steps runs every time.

3. Deterministic Steps:

   • Steps are memoized by their ID (1st arg). IDs must be unique and stable.
   • Do not dynamically generate step IDs unless you know what you are doing (e.g., inside loops with index).

4. Return Data from Steps:

   • If you need a value later, return it from the step.
   • ❌ Bad: let userId; await step.run(..., () => { userId = ... })
   • ✅ Good: const userId = await step.run(..., () => { return ... })

Core Patterns

1. Multi-Step Execution

Wrap all logic in steps to ensure retriability and resumability.

export const processOrder = inngest.createFunction(
  { id: "process-order" },
  { event: "shop/order.created" },
  async ({ event, step }) => {
    // 1. Step: Validate (Retriable)
    const user = await step.run("get-user", async () => {
      return await db.users.findById(event.data.userId);
    });

    // 2. Step: Sleep (Durable pause)