A transaction is a set of database reads and writes that is handled as a unit with a few crucial properties. First, all reads in the transaction see the same snapshot of the database (e.g. do not see changes to the data resulting from other transactions executing concurrently). Second, the writes within a transaction either all succeed or all fail. (Failure might be caused, for example, by a connection loss.) Lastly, after a transaction succeeds (commits), the writes are permanently stored. These properties of transactions (called Atomicity, Consistency, Isolation, and Durability) are the fundamental “ACID” guarantees. We at FoundationDB think that support for ACID transactions is much more than a nice extra feature