Even I had the same question - https://news.ycombinator.com/item?id=17916769 .

I'm aware of the following options:

1. PouchDB(CouchDB HTTP protocol) or RxDB

2. DexieJS(Indexed DB Wrapper)

3. Mozilla LocalForage(Indexed DB Wrapper)

4. OrbitJS(Indexed DB Wrapper using JSONAPI)

5. Google Lovefield(Relational equivalent)

6. GunJS

7. NanoSQL

Would love to hear from somebody with a production exp. in these technologies.