Who holds the pen (consensus & Raft)

The System Design spine’s episode on who is allowed to write. The copy clerks (database replication) said the stall may have “only ONE new master” and never said who picks it. This is who picks it, and what the picking cannot protect.

Before you start. The stall in this lesson is the chai stall the System Design spine has been running: five clerks behind the counter, each keeping a copy of the register in a book of their own, and one pen that decides who is allowed to write in it. The copy clerks (database replication) is where those clerks came from, and The cut phone line (CAP, done properly) is the rule that when the wire between two copies is cut, you must choose between answering and being right.