System Design Questions:

1. Table User with userInfo and another table User_Relationship with columns as User1 ( Indexed ) and User2 ( Indexed ) and relationship ( with values as Friend ). The User_Relationship could be bi-directional so i.e., if A is friend of B then USER_Relationship table can have it as A, B, Friend as a row or B,A, Friend. How do you find a good scalable solution to find count of friends for a given user

2. There are notifications sent out for documents upon they are signed by the users. The documents are in millions and we have the document ids in the table. However there are failed notifications and due to system issue they are not even captured on the logs. Only the sent notifications are logged. How do you scale the solution to identify all the failed notifications.

3. Google document sharing application has a round robin scheme of serving by the load balancer. Do you foresee any issue? If so how do you overcome it?

4. There is a graph of node capabilities across various nodes and will have to identify the throughput of the entire system through the nodes.

5. In what cases do you choose strong consistency vs eventual consistency and there are 3 scenarios
   a. In case of banking application where there are deposits and payments
   b. Metadata retrieval for media streaming
   c. Data analytics for # of viewers etc.,