TIL Mongodb

Replication

• Read preference defaults to primary unless the primary specifies otherwise
• Mean time for a primary election is 12 seconds
• Replication is an asynchronous process between primary and secondaries
• Arbiters should be votes: 1, priority: 0 so they can never become primary but are able to participate in elections
  • Not a desirable topology because a replset can come under pressure if you lose a data bearing node
• Priority 0 members cannot become primary and cannot trigger elections
  • They can acknowledge writes for writeConcern: n