> I get how it helps ordering of transactions but I am confused if it is used in making transactions atomic across machines ? AIUI, you cannot quiet think of i

> I get how it helps ordering of transactions but I am confused if it is used in making transactions atomic across machines ? AIUI, you cannot quiet think of it like a regular database where a particular row has a particular value which would necessitate only one writer doing (atomic) updates at a time. Rather it is a MVCC-like database and a bit like an append-only log: as many writers as needed can write and there are 'multiple values' for each row. The "actual" value of the row is the one with the highest transaction ID / timestamp. So updates can happening without (atomic) locking by just adding to the value(s) that already exist. When reading, applications just generally get served the value with the highest-value timestamp, and since time is synchronized to such a tiny interval, it is a reasonably sure bet that the highest value is the most recent transaction. This is similar in concept to a vector clock (see also Lamport): * https://en.wikipedia.org/wiki/Vector_clock https://en.wikipedia.org/wiki/Vector_clock But instead of logical clocks with 'imaginary time', 'real time' is used down to the sub-microsecond level.