When I started Tweet the Tube it was a small PHP application triggered by a cron job.
This had been fine for years, until I decided to ditch my hosting provider as it was costing me $20 per month.
I knew that I wanted to move into AWS, but running a nano EC2 instance would still cost me $5 per month. Not a lot of money but still more than I wanted to pay for such a small application.
Then I found out that AWS Lambda had a free tier. Better yet it meant no servers to manage. Seemed like a win-win to me!