Can't really agree with that. Although most of my experience and expertise is with mobile game development, I think that I've read at least 5 blog posts and articles that explained that all connection strings, usernames and passwords (aside from something really trivial for local testing) should always be read from environment variables and never be hardcoded, and arguments were convincing enough. So, even if I haven't worked with Heroku before, I would look for a way to get this url in a service-provided environment variable.

Also, I would look to configure all components to fail loudly, so that if something wouldn't connect to Redid, my server just wouldn't launch.

I'm not trying to say that I'm better or smarter than OP: I've actually tried learning bioinformatics, but dropped out of uni 14 years ago, realising that my brain is just not created for anything biology-related. Rather my point is, many of these problems (and problems I've seen junior developers struggling with) are not some arcane knowledge that you should just learn by heart (like all of those awful genus names in Latin, or all the enzymes in the dreadful ATP scheme that I still have nightmares of sometimes), but a logical extension of more basic and universal principles that actually make total sense once you think about them.