How we run checks

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Checkly runs your API & browser checks every x minutes, based on an interval you select. We have different minimum intervals for each check type:

  • API checks can be scheduled to run every 1 minute.
  • Browser checks can be scheduled to run every 10 minutes.

You can select one or more data center locations to run your check from. We advise to always select at least 2 locations. There are two reason for this:

  1. Redundancy: we might have an issue in one location, but not the other.
  2. Double checking: if your check fails and you have “double check” enabled we will retry the check from the other location.

A picture is a thousand words:

monitoring and alerting pipeline

  1. A cron process picks up a check based on its schedule, say every 5 minutes.
  2. The script is put into a queue to be run from the next configured data center location. If the check is an API check and has a setup script, the setup script is executed.
  3. If the check fails and “double check” is enabled, the check is retried once in the same location and in a different location. The other location is picked, at random, from all the configured locations.
  4. If the check is an API check and has a teardown script, the teardown script is executed. Teardown scripts are run before any assertions are validated.
  5. The result is stored in our central database and any alerts are sent where applicable.

SSL Checks

SSL monitoring occurs in three steps:

  1. When configuring API checks or browser checks, we automatically determine what domains can/should be checked for SSL certificate expiry.

  2. Once a day, we check all your configured domains.

  3. If the expiry date hits a threshold in your alert settings, we send an alert.

If you have multiple checks on the same domain (e.g. and we deduplicate them just for SSL checking.