Transactions

Data Systems track.

This lesson is about what happens when two things touch the same row, or the same rule, at once, and why the fix that catches all of it is expensive on purpose.

Before you start. The previous lesson, Encoding and Schema Change, turned a record into bytes in an agreed format, so two programs changing independently could still read each other’s data. Here everything stays on one machine; you only need to read a row of a table and picture two people reading the same one at once.