I am concerned about alphavantage and cautious about using their service.
The information contained on their website is very sparse. As I mentioned in my first post, it is not clear what their business model is -- who supports the service, where their data comes from, how they make the money they need to provide the service.
On three separate days I sent three separate emails with three separate Subjects to alphavantage. There has been no response. The emails did not bounce, but they were not acknowledged. The information on the website has not been improved.
These are not good signs.