ChannelPulse
Replication, quorums, and what "consistent" means to your interviewer
One copy of your data is a single point of failure; two copies are a disagreement waiting to happen. This derives what replication buys, what a quorum guarantees and — more importantly — what it does not, and how to answer "is this strongly consistent?" without reciting CAP.
What you'll be able to do
- State what a quorum guarantees, and construct the case where R + W > N still returns a stale read
- Choose between single-leader, multi-leader, and leaderless replication by naming the write conflict each one has to resolve
- Distinguish replication lag from inconsistency, and name the three read-your-writes fixes
- Answer a CAP question in terms of a specific operation rather than a whole system
Before this: picking-a-datastore
The rest of this lesson is in the app
One copy of your data is a single point of failure; two copies are a disagreement waiting to happen. This derives what replication buys, what a quorum guarantees and — more importantly — what it does not, and how to answer "is this strongly consistent?" without reciting CAP. This walkthrough runs about 24 minutes, with runnable code you can edit and re-run as you read.
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