the.com/cap theorem
pick two: consistency, availability, partition tolerance — the network will make the third choice for you.
means in a distributed database, when the network splits you can't have perfectly up-to-date data everywhere and keep answering requests, so you must sacrifice one.
from conjectured by eric brewer at a 2000 podc keynote, formally proved in 2002 by seth gilbert and nancy lynch, becoming the founding excuse of nosql marketing.
real constraintpartition tolerance isn't optional, networks just fail
actual tradeoffreally just consistency versus availability during a partition
famous casualtyamazon dynamo chose availability, inspired cassandra
brewer's regretlater said the 'pick two' framing oversimplifies badly