About 9 years ago, I built an online system for taking applications for people looking to get their kids into a charter school in North Carolina.
Over the ensuing years, I will say that the system has been very solid. The biggest problem we had was in using shared hosting. It turns out that Email black-listing spans customer who are on the same server. The application sends a confirmation to each registrant, and on shared hosting, if another person is sending spam or causing your IP address to get black-listed, you are an innocent bystander. I desperately pled to the hosting company (GoDaddy) and my requests fell on deaf ears.
So I moved to Amazon Web Services. My experience was and is night and day. I did have to learn lots about hosting managing web servers, sending emails the AWS way and much more, but having my own server where I can add capacity in a few clicks is a game changer.