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by gchpaco
3604 days ago
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Depends on the database, but Cassandra, for example, has quorum mode for writes, which requires a majority of the cluster members ack the write. This can be enabled on a per-query basis, and also for reads. The other way of doing it is things like CRDTs (https://en.wikipedia.org/wiki/Conflict-free_replicated_data_...) which have a join operation for any two data values. You have to keep it in the back of your mind that it's a thing, but working without consistency can be done. |
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CRDTs do one thing... they mitigate the issue of "lost updates". All acknowledged writes will be represented in the results of a query and no "winner" strategy is involved that would cause some acknowledged writes to be possibly incorrectly dominated by others and thus lost.
Quorum (strict) just provides a very, very, very weak form of consistency in the case of concurrent readers/writers (RYW) and just very, very weak consistency in the case of serialized readers/writers (RR).
My personal opinion is that any eventually consistent distributed database that doesn't have built-in CRDTs, or the necessary facilities to build application-level CRDTs, is a fundamentally dangerous and broken database because unless all you ever write to it is immutable or idempotent data, you're going to have your database silently dropping data during operation.