Everything You Know About MongoDB Is Wrong

https://developer.mongodb.com/article/everything-you-know-is-wrong

by ayush--s • 6 years ago

6 2 6 years ago

developer.mongodb.com

spccdt• 6 years ago

“...But this is not the case! Some of these parts have never been the case - MongoDB has never been "eventually consistent" - updates are streamed and applied sequentially to secondary nodes, so although they might be behind, they're never inconsistent.”

Isn’t this exactly what eventual consistency is? Or am I missing something? If a client performs a read query on the primary, followed by a second read on a secondary (perhaps because the primary server is unavailable), then it seems clear that there could be a chance of reading stale data.

asya999• 6 years ago

There are systems that accept writes in multiple places (to the same object). So you could read writes applied in different order on different nodes, though in theory eventually all the nodes will converge on the same object value. This is akin to dirty writes, a consistency level no actual database allows. That’s the distinction between stale and ... eventually consistent.

TL;DR stale and consistent is better than inconsistent.

Everything You Know About MongoDB Is Wrong

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