https://docs.aws.amazon.com/lambda/latest/dg/services-cloudw...
Firebase is really easy to get started with so I'd recommend it for prototyping if you're not keen on AWS or Google Cloud.
But it depends on what you already have. I have a side project with a ec2 running node so I just use cron from npm (rather than the os cron) to do the trick and pm2 to keep that node running.