How to Design a user system which includes login, register, queries, relationship

Now we are implement the 4S analysis method：

Scenario: login register query, user info change request
and we have to support 100M DAU
for login, register, info change:
Average QPS: 100
Peak QPS: 100 * 3 = 300
for query:
Average APS: 100K
Peak QPS: 100K * 3 = 300K

Service:
login----AuthService
query, user info change request: UserService
friendship network: storage friendship

Storage:
SQL or NoSQL?
if NoSQL, then Memcached or Redis?
how to design the table?

Scale:
more server to handle high volume of user request, but in the same time, problems are raised: single point failure