Firebase is a good idea. But also just using local storage for less important user data (like has_seen_welcome) and having your SaaS store stuff (like 40% sales

Firebase is a good idea. But also just using local storage for less important user data (like has_seen_welcome) and having your SaaS store stuff (like 40% sales) in a settings file or something like that still works. Don't underestimate the value of keeping things simple and reducing dependencies.