Replication.
Keeping copies of your data on several machines, so a failure or a far-away reader is no big deal.
- 1
One ledger on one machine is a single point of failure — lose it and everything is gone.
- 2
So you photocopy it, keeping a copy in every branch office.
- Record it here.3
Writes go to one leader copy that owns the latest truth.
- 4
The leader streams its change log out so every follower stays in sync.
- 5
Reads can come from any copy, spreading the load and serving nearby readers fast.
- 6
The catch is lag: a follower is always a little behind, so it can briefly show stale data.
Semicolony semicolony.dev/eli5/replication/comic