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What you describe is read uncommitted. From your own docs:

> A third party that performs cross-database reads can observe partial commits while a 2PC transaction is in progress.

Regardless of rollback status, the in-flight transaction will not be observed correctly across shards, for example, with a cross-shard join. It doesn't matter what the consistency guarantee within a shard is; this is not ACID nor is it serializable.

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Its not, its still read committed. Its the same thing as if you had to read from two rows in a transaction, and your isolation was read committed, and both those rows would be modified by a different transaction. Its possible you read the first row, a transaction is committed and then you read the second row with the updates from the transaction. You have just read a partial commit. It is ACID and it is not serializable, the thing is MySQL lets you use higher levels of isolation like repeatable read or serializable which are very useful and today Vitess can't guarantee that in a 2PC.

Y'all really should hire me at some point. I've been building out transactional analysis tooling for Jepsen that can help distinguish between exactly these cases. :-)

Yes! We have it on our todo list to have you test out Vitess.

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