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  1. Jul 2021
    1. One of the fundamental goals of a blockchain is resolving the “double spend” problem. In a nutshell, this means preventing someone from sending the same coin to two people. However, beyond just simple spend transactions, it applies any time two transactions want to update the same state. This could be someone trying to duplicate Bitcoin, or two people trying to buy the same CryptoKitty. For the sake of generality, we’ll call it the “double update” problem. Fundamentally it’s about ordering: when we see two things, how do we decide which is first, and what happens to the second one?

      The double spend problem is a subset of what can be called the double update problem. How do we order two updates to the same state?