Replication
3 engineering logs on Replication. Newest first.
- R plus W greater than N is the arithmetic that decides your consistency
Why quorum overlap is the whole guarantee, what W equals one actually costs, and why the inequality holding does not save you from concurrent writes that no read can order.
- The replica lag you do not measure is the one serving checkout
Why byte lag reads zero on a broken replica, how read-your-writes breaks the moment you add a read replica, and why routing all reads to replicas is a correctness decision rather than a scaling one.
- fsync is the only thing between you and data loss, and it is slower than you think
Why a successful write() means nothing, what fsync actually costs in the cloud, and why synchronous_commit off and fsync off are not the same knob despite being discussed as if they were.