Thanks so much for the reply, it saved me a few hours of trying it out at the very least! Of course, I hope there is support for Memorystore on App Engine eventually. Thank you.
I apologize for bringing up something that is offtopic here but I am really glad to have read your comment.
Last I read in the docs, Memorystore was not accessible through the AppEngine Standard Environment, which was rather disappointing to me.
I was wondering if just providing the App Engine Standard Environment with the Redis instances address and credentials, along with a service account or IP whitelist for access, would not suffice to be usable there as well. If I'm not wrong, something similar is done in Flexible Environment according to the docs.