Summary

Stores SSO info such as userid:pwd and userid:appdata
based on BerkleyDB & Paxos.
Favors availability and consistency
Consistent read and writes must go through master
- Writes always use majority Quorum
- Reads use Leases and local state
  - Given there is only 1 primary node choosen by quorum he obtains the lease.
  - During the period of the lease there cannot be another election. E.g. if the master is partitioned away from the rest of the system, other nodes cannot elect another node before the lease expires. This guarantees that the master is the only master and can serve reads/writes .
    - What happens if there is such a partition, someone wrote stuff to master and then lease expired. A new election post that could elect another node as a primary which would mean writes to the old master are lost ?
Philosophy of delaying complexity until necessary
Better to design for correctness in as many errors as possible than to place bets on how rare certain error scenarios are.