I want to develop a mobile app with Cloud Firestore as backend. It's good until I realize need to implement FullTextSearch, and Firestore doesn't support it natively. Although they advise to use Algolia but at this time I'm not willing to pay for it.

Therefore, I'm thinking about using the built-in tool from Google Cloud. Since this app is online-only, the offline & sync are not a top priority, so how about use Google Cloud SQL? Or, do you recommend any stack for me? Thanks for your advice.