Syntax
INSERT INTO users (id, email) VALUES (?, ?) IF NOT EXISTS;
UPDATE counters SET n = 10 WHERE id = ? IF n = 9;Advertisement
Cost
4 round trips vs 1 for normal. Paxos: prepare + promise + accept + accepted. Much slower.
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Serial consistency
SERIAL or LOCAL_SERIAL. LOCAL_SERIAL: quorum in local DC only. Faster multi-DC. Standard for single-DC LWT.