Glossary · Triggers & webhooks
Cron expression
Also called: cron syntax, crontab, cron schedule
A cron expression is a compact five-field string (minute, hour, day of month, month, day of week) that tells a scheduler exactly when to run a job.
Cron comes from the Unix job scheduler of the same name. Each field is a number, a range, a list or * for "every":
┌ minute (0-59)
│ ┌ hour (0-23)
│ │ ┌ day of month (1-31)
│ │ │ ┌ month (1-12)
│ │ │ │ ┌ day of week (0-6, Sunday = 0)
* * * * *Examples worth memorizing
| Expression | Runs |
|---|---|
30 7 * * 1-5 | 7:30 on weekdays |
0 8 * * 1 | 8:00 every Monday |
*/15 * * * * | Every 15 minutes |
0 2 1 * * | 2:00 on the first of each month |
0 9-17 * * 1-5 | On the hour, 9 to 5, weekdays |
The pitfalls
- Time zone.
0 8 * * 1means 8:00 somewhere. Classic cron uses the server's zone; set the schedule's zone explicitly, or your Monday report arrives at 3am. - Daylight saving. Jobs scheduled between 1:00 and 3:00 can run twice or not at all on the change-over night. Avoid that window for anything that sends.
- Day-of-month and day-of-week together. In standard cron, setting both means "either", not "both".
0 9 1 * 1runs on the 1st and every Monday.
In Fluxo Flow
The Scheduled trigger offers one-time, daily, weekly and monthly schedules, or a standard cron expression, in the time zone you pick, and shows the next run time as you type. You can limit runs to allowed days and a time window, and set start and end dates. How often a schedule can run depends on the plan; a schedule faster than your plan allows is refused when you activate it. Scheduled runs start within about a minute of their time.
Read next
Related terms
- TriggerA trigger is the event that starts a workflow run: a person pressing Run, a schedule coming due, a webhook arriving, or a new record or event in a connected app.
- Polling vs webhooksPolling means your system asks another system for new data on a fixed schedule; webhooks mean the other system pushes each event to you the moment it happens.
- WorkflowA workflow is a repeatable sequence of steps, started by a trigger, that turns an input (a form, an invoice, a new deal) into an outcome, with defined rules for each decision along the way.
- Dead-letter queueA dead-letter queue is a holding place for messages or items that couldn't be processed after all retries, kept aside with their error so a person can inspect, fix and replay them instead of losing them.
- Context windowA context window is the maximum number of tokens a language model can take into account in a single request, counting the instructions, the input data and the reply it writes.