Inngest Steps
Build robust, durable workflows with Inngest's step methods. Each step is a separate HTTP request that can be independently retried and monitored.
These skills are focused on TypeScript. For Python or Go, refer to the Inngest documentation for language-specific guidance. Core concepts apply across all languages.
Core Concept
🔄 Critical: Each step re-runs your function from the beginning. Put ALL non-deterministic code (API calls, DB queries, randomness) inside steps, never outside.
📊 Step Limits: Every function has a maximum of 1,000 steps and 4MB total step data.
// ❌ WRONG - will run 4 times
export default inngest.createFunction(
{ id: "bad-example" },
{ event: "test" },
async ({ step }) => {
console.log("This logs 4 times!"); // Outside step = bad
await step.run("a", () => console.log("a"));
await step.run("b", () => console.log("b"));
await step.run("c", () => console.log("c"));
}
);
// ✅ CORRECT - logs once each
export default inngest.createFunction(
{ id: "good-example" },
{ event: "test" },
async ({ step }) => {
await step.run("log-hello", () => console.log("hello"));
await step.run("a", () => console.log("a"));
await step.run("b", () => console.log("b"));
await step.run("c", () => console.log("c"));
}
);step.run()
Execute retriable code as a step. Each step ID can be reused - Inngest automatically handles counters.
// Basic usage
const result = await step.run("fetch-user", async () => {
const user = await db.user.findById(userId);
return user; // Always return useful data
});
// Synchronous code works too
const transformed = await step.run("transform-data", () => {
return processData(result);
});
// Side effects (no return needed)
await step.run("send-notification", async () => {
await sendEmail(user.email, "Welcome!");
});✅ DO:
- Put ALL non-deterministic logic inside steps
- Return useful data for subsequent steps
- Reuse step IDs in loops (counters handled automatically)
❌ DON'T:
- Put deterministic logic in steps unnecessarily
- Forget that each step = separate HTTP request
step.sleep()
Pause execution without using compute time.
// Duration strings
await step.sleep("wait-24h", "24h");
await step.sleep("short-delay", "30s");
await step.sleep("weekly-pause", "7d");
// Use in workflows
await step.run("send-welcome", () => sendEmail(email));
await step.sleep("wait-for-engagement", "3d");
await step.run("send-followup", () => sendFollowupEmail(email));step.sleepUntil()
Sleep until a specific datetime.
const reminderDate = new Date("2024-12-25T09:00:00Z");
await step.sleepUntil("wait-for-christmas", reminderDate);
// From event data
const scheduledTime = new Date(event.data.remind_at);
await step.sleepUntil("wait-for-scheduled-time", scheduledTime);step.waitForEvent()
🚨 CRITICAL: waitForEvent ONLY catches events sent AFTER this step executes.
- ❌ Event sent before waitForEvent runs → will NOT be caught
- ✅ Event sent after waitForEvent runs → will be caught
- Always check for
nullreturn (means timeout, event never arrived)
// Basic event waiting with timeout
const approval = await step.waitForEvent("wait-for-approval", {
event: "app/invoice.approved",
timeout: "7d",
match: "data.invoiceId" // Simple matching
});
// Expression-based matching (CEL syntax)
const subscription = await step.waitForEvent("wait-for-subscription", {
event: "app/subscription.created",
timeout: "30d",
if: "event.data.userId == async.data.userId && async.data.plan == 'pro'"
});
// Handle timeout
if (!approval) {
await step.run("handle-timeout", () => {
// Approval never came
return notifyAccountingTeam();
});
}✅ DO:
- Use unique IDs for matching (userId, sessionId, requestId)
- Always set reasonable timeouts
- Handle null return (timeout case)
- Use with Realtime for human-in-the-loop flows
❌ DON'T:
- Expect events sent before this step to be handled
- Use without timeouts in production
Expression Syntax
In expressions, event = the original triggering event, async = the new event being matched. See Expression Syntax Reference for full syntax, operators, and patterns.
step.waitForSignal()
Wait for unique signals (not events). Better for 1:1 matching.
const taskId = "task-" + crypto.randomUUID();
const signal = await step.waitForSignal("wait-for-task-completion", {
signal: taskId,
timeout: "1h",
onConflict: "replace" // Required: "replace" overwrites pending signal, "fail" throws an error
});
// Send signal elsewhere via Inngest API or SDK
// POST /v1/events with signal matching taskIdWhen to use:
- waitForEvent: Multiple functions might handle the same event
- waitForSignal: Exact 1:1 signal to specific function run
step.sendEvent()
Fan out to other functions without waiting for results.
// Trigger other functions
await step.sendEvent("notify-systems", {
name: "user/profile.updated",
data: { userId: user.id, changes: profileChanges }
});
// Multiple events at once
await step.sendEvent("batch-notifications", [
{ name: "billing/invoice.created", data: { invoiceId } },
{ name: "email/invoice.send", data: { email: user.email, invoiceId } }
]);Use when: You want to trigger other functions but don't need their results in the current function.
step.invoke()
Call other functions and handle their results. Perfect for composition.
const computeSquare = inngest.createFunction(
{ id: "compute-square" },
{ event: "calculate/square" },
async ({ event }) => {
return { result: event.data.number * event.data.number };
}
);
// Invoke and use result
const square = await step.invoke("get-square", {
function: computeSquare,
data: { number: 4 }
});
console.log(square.result); // 16, fully typed!Great for:
- Breaking complex workflows into composable functions
- Reusing logic across multiple workflows
- Map-reduce patterns
Patterns
Loops with Steps
Reuse step IDs - Inngest handles counters automatically.
const allProducts = [];
let cursor = null;
let hasMore = true;
while (hasMore) {
// Same ID "fetch-page" reused - counters handled automatically
const page = await step.run("fetch-page", async () => {
return shopify.products.list({ cursor, limit: 50 });
});
allProducts.push(...page.products);
if (page.products.length < 50) {
hasMore = false;
} else {
cursor = page.products[49].id;
}
}
await step.run("process-products", () => {
return processAllProducts(allProducts);
});Parallel Execution
Use Promise.all for parallel steps.
// Create steps without awaiting
const sendEmail = step.run("send-email", async () => {
return await sendWelcomeEmail(user.email);
});
const updateCRM = step.run("update-crm", async () => {
return await crmService.addUser(user);
});
const createSubscription = step.run("create-subscription", async () => {
return await subscriptionService.create(user.id);
});
// Run all in parallel
const [emailId, crmRecord, subscription] = await Promise.all([
sendEmail,
updateCRM,
createSubscription
]);
// Optimization: Enable optimizeParallelism for many parallel steps
export default inngest.createFunction(
{
id: "parallel-heavy-function",
optimizeParallelism: true // Reduces HTTP requests by ~50%
},
{ event: "process/batch" },
async ({ event, step }) => {
const results = await Promise.all(
event.data.items.map((item, i) =>
step.run(`process-item-${i}`, () => processItem(item))
)
);
}
);See inngest-flow-control for concurrency and throttling options.
Chunking Jobs
Perfect for batch processing with parallel steps.
export default inngest.createFunction(
{ id: "process-large-dataset" },
{ event: "data/process.large" },
async ({ event, step }) => {
const chunks = chunkArray(event.data.items, 10);
// Process chunks in parallel
const results = await Promise.all(
chunks.map((chunk, index) =>
step.run(`process-chunk-${index}`, () => processChunk(chunk))
)
);
// Combine results
await step.run("combine-results", () => {
return aggregateResults(results);
});
}
);Key Gotchas
🔄 Function Re-execution: Code outside steps runs on every step execution ⏰ Event Timing: waitForEvent only catches events sent AFTER the step runs 🔢 Step Limits: Max 1,000 steps per function, 4MB per step output, 32MB per function run in total 📨 HTTP Requests: With serve, use checkpointing to reduce HTTP requests 🔁 Step IDs: Can be reused in loops - Inngest handles counters ⚡ Parallelism: Use Promise.all, consider optimizeParallelism for many steps
Common Use Cases
- Human-in-the-loop: waitForEvent + Realtime UI
- Multi-step onboarding: sleep between steps, waitForEvent for user actions
- Data processing: Parallel steps for chunked work
- External integrations: step.run for reliable API calls
- AI workflows: step.ai for durable LLM orchestration
- Function composition: step.invoke to build complex workflows
Remember: Steps make your functions durable, observable, and debuggable. Embrace them!