I am sorry to be that guy but why ruby? I feel that Lago is a good idea but ruby usage is in a downward trend and few developers want to invest time in ruby projects these days. Was node or python considered?
That's a fair question!
To be honest, it was a no brainer choice for us since we were 2 engineers at the beginning with 10y exp on Ruby, we wanted to be focused on our product and not on the tech we could use.
Ruby ecosystem is still a very good choice imo, as Python or NodeJS or any other language could also be!
I have the strong opinion that regardless the language you use, you will always face the same problems, so go with what you're familiar with and let's focus on what you want to do. I can swear that we had some headaches about our core billings features, if we had a tech we did not master, we may have lose all our hairs!
The only downside I can see is recruitment, it can be harder to find experienced ruby developers, but well, if it's the only one we have, I'm pretty happy with it!