I have done with before, ran and one man b2b saas platform with 30clients from around the world. Infrastructure was the easiest part. We where processing roughly 100million messages a day, about 5 nodes. Monitoring was good, application performance tracking was good. Business ran for close to 7 years, making about 1.3mill a year on an average year.
Yes, I no longer have the business. It got harder and harder to compete with larger players as the market begin to attract more players. I sold of the business to a larger company (just contracts and not tech).
Hard part was support. Due to my clients being from around the world, sometimes they need help with items and expect a certain level of service, such and responses to support questions with in 24 hours or sometimes sooner. This required me to 90% of the time forward the inquiry to the a upstream vendor and that took time to collateral the right data to vendor (from the client's inquiry).
I did end up hiring a support personal for help to give me some breathing room on the weekends.
