---
title: Jobs and cron
description: A Schedule starts a Workflow's Runs on a calendar or an interval; every fire is an engine timer, and one instant starts at most one Run.
type: tutorial
product: jobs
summary: What a Schedule is, what a fire is not, and the surface that runs schedules today.
updated: 2026-09-28
order: 0
---

A Schedule starts Runs of a Workflow on a calendar or an interval. Nothing
calls it: every fire is an engine timer, so a schedule that is due fires even
while nothing of yours is running.

`(schedule, intended time)` is the Run identity. One instant starts at most
one Run, however many times a wake is delivered, so a retry or a duplicated
wake cannot start the same instant's Run twice. And a fire is not a Run
result: the fire is what starts the Run, and how that Run ended is the Run's
own outcome.

## What you set on a Schedule

<PropertyTable
	properties={[
		{
			name: 'calendar.kind',
			type: 'string',
			description: 'The trigger: rate, a fixed period, or cron, an expression.',
		},
		{
			name: 'calendar.everySeconds',
			type: 'number',
			description: 'The period of a rate, 1 to 31536000 seconds.',
		},
		{
			name: 'calendar.expression',
			type: 'string',
			description: 'The 5- or 6-field cron expression of a cron calendar.',
		},
		{
			name: 'calendar.timezone',
			type: 'string',
			description: 'The IANA time zone the calendar is read in.',
		},
		{
			name: 'overlap',
			type: 'string',
			description: 'What a fire does while the previous Run is still running: skip, buffer_one or allow.',
		},
		{
			name: 'catchUp',
			type: 'string',
			description: 'What a missed fire does: skip, last_only (only the most recent), or bounded by maxTicks or maxAgeSeconds.',
		},
		{
			name: 'target',
			type: 'object',
			description: 'Where the fire lands: an http target (an https url, a method, signed set to true), or execute, which names a jobId and its expectedRevision.',
		},
		{
			name: 'retry.maxAttempts',
			type: 'number',
			description: 'How many times a fire is retried.',
		},
		{
			name: 'pause',
			type: 'bool',
			description: 'Whether fires are paused.',
		},
	]}
/>

A rate's first due time is one interval after the schedule is created, so a
schedule made now with a 30-second rate first fires 30 seconds from now.

## Where the Runs go

On the surface that runs today, a fire lands on an HTTP target: a signed
request to an https URL, in the method the target states. [HTTP
targets](/docs/jobs/targets) is the receiver's side of that. The declared
`schedules` collection describes the same object the other way round — its
Schedule names the Workflow to start, in the same environment.

## The surface that runs schedules today

Schedules run on the Sylphx Compute API, a service of its own with its own
base URL and its own key scopes, called with `fetch`. The SDK's `workflows`
module covers Workflow Runs, not these schedules. A request presents a
Sylphx Access key, `Authorization: Bearer sylphx_sk_…`, and schedules take the
`workflows:read` and `workflows:write` scopes.

The one API's `schedules` collection is the Schedule Resource as declared —
the name pattern, the spec, `pause` and `resume` — and
[the `schedules` collection](/docs/api/schedules) is where that shape is
written down. The calls that run today are the Compute API's.

<KeyValue
	items={[
		{ key: 'Base URL', value: 'https://api.compute.sylphx.com', mono: true },
		{ key: 'Create', value: 'POST /v1/schedules', mono: true },
		{ key: 'Read one', value: 'GET /v1/schedules/{id}', mono: true },
		{ key: 'Delete', value: 'DELETE /v1/schedules/{id}', mono: true },
		{ key: 'Scopes', value: 'workflows:read, workflows:write', mono: true },
		{ key: 'Identity', value: 'identity.resourceId, identity.revision', mono: true },
		{ key: 'Declared name', value: 'orgs/{org}/projects/{project}/envs/{env}/schedules/{schedule}', mono: true },
	]}
/>

The fields on that wire are camel case — `everySeconds`, `catchUp`,
`lastTick`, `deadLetters` — and an answer names the authority that gave it. An
error carries a code and a message rather than a status alone:
`{"error": {"code": "conflict", "message": "…"}, "product": "Sylphx Compute", "authority": "compute"}`.

<RelatedDocs
	links={[
		{
			href: '/docs/jobs/quickstart',
			label: 'Quickstart',
			description: 'Create a schedule, take the wake receipt, and delete it again.',
		},
		{
			href: '/docs/jobs/schedules',
			label: 'Schedules',
			description: 'The identity rule, the tick states, pause, and the delete fence.',
		},
		{
			href: '/docs/jobs/targets',
			label: 'HTTP targets',
			description: 'Where a fire lands, and what the receiver answers.',
		},
		{
			href: '/docs/api/schedules',
			label: 'The schedules collection',
			description: 'The Schedule Resource as declared, with every method and example.',
		},
	]}
/>