Imagine assigning some value to a variable, reading it back immediately after, and finding out that somehow the write had no effect at all — madness!

This is precisely what can happen when you are using a distributed data store with weak consistency guarantees. “But wait, aren’t databases supposed to take care of consistency issues for me?” I hear you ask. Whether an update becomes visible sooner rather than later depends on the guarantees offered by the database.

Some databases come with counter-intuitive consistency guarantees to provide high availability and performance. Others have knobs that allow you to chose whether you want better performance or stronger guarantees, like Azure’s Cosmos DB and Cassandra. …


Roberto Vitillo

Principal Software Engineer @ Microsoft —

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