There is absolutely no real way to do that. Each user has relationships with other users. All relationships need to be stored. There just are some 70 million of them. I can cut that in half by storing only relationships on one person's part, but that's still 35 million, it translates into 2 queries instead of just 1, and the point still stands.
>> 380.000 users, that's over 70 million database entries
how does 380,000 users automatically translate to over 70 million rows? Why does each user need 190 rows? Maybe you need to re-think your database design if that is the case.