Post author here!<p>The on disk part of the &quot;switch&quot;, our transaction record, can only be accessed internally. There are only a small number of operations to perform on it - create it, read its value, and a small number of deterministic &quot;read-then-write&quot; operations. For example, in the case of an &quot;abandoned&quot; transaction, a later transaction may want to read the abandoned transaction record, see if it is still &quot;pending&quot;, and then mark it as &quot;aborted&quot; if it is.<p>Our runtime orders all such operations on the same record so that they are completely sequential - that is, even for a &quot;read-then-write&quot; operation, it must completely finish before any other operation can occur on that key.  This is done using basic runtime synchronization primitives (mutexes, channels, etc).