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Links for 2017-06-30

  • Don’t Settle For Eventual Consistency

    Quite an argument. Not sure I agree, but worth a bookmark anyway…

    With an AP system, you are giving up consistency, and not really gaining anything in terms of effective availability, the type of availability you really care about.  Some might think you can regain strong consistency in an AP system by using strict quorums (where the number of nodes written + number of nodes read > number of replicas).  Cassandra calls this “tunable consistency”.  However, Kleppmann has shown that even with strict quorums, inconsistencies can result.10  So when choosing (algorithmic) availability over consistency, you are giving up consistency for not much in return, as well as gaining complexity in your clients when they have to deal with inconsistencies.

    (tags: cap-theorem databases storage cap consistency cp ap eventual-consistency)

  • Delivering Billions of Messages Exactly Once · Segment Blog

    holy crap, this is exactly the wrong way to build a massive-scale deduplication system — with a monster random-access “is this random UUID in the db” lookup

    (tags: deduping architecture horror segment messaging kafka)