> That sounds like loading the entire database every time
Yup, we do perform computation over the entire database for every read - there is zero correlation between the server's work and the client's query. We currently serve queries to a 1 GB database in under 1 second. For much larger databases (100+ GB), this becomes more a question of cost: we can stay fast (1 sec) with more expense, or go slower (e.g. 5 sec) and stay cheap.
> Cryptographic proof that the server is not spying
If you trust your client software [0], then you can be sure that your request isn't decrypted anywhere outside your device. Even a malicious Blyss server cannot determine your query, because it never got a chance to see it.
[0] This level of security depends entirely on having a trusted client. Our client software is open source, and we plan to have it formally audited. We'll also publish signed desktop apps so you can be sure that you're running the same client every time.