I recently tried to schedule an AWS Lambda defined through a SAM template to run every 10 minutes. I used some online cron expression builders but the syntax would not work with Cloudwatch.
Somehow, I missed this reference in the Schedule Expressions for Rules. The online expression builder puts * for both day of the month and day of the week.
You cannot use * in both the Day-of-month and Day-of-week fields.
If you use it in one, you must use ? in the other.
Here is the expression that worked:
Schedule: cron(0,10,20,30,40,50 * ? * * *)