Indeed I did not–just long enough to “reset”–but I completely understand any reticence! And I had no idea that the Handmade powers that be are so quick to get antsy. 
If vacation listings are individually marked, it might not be bad code but inefficient, and the race condition applies.
If vacation mode is checked before the order is displayed and the race condition has affected the multiple copies of the seller account information, that is definitely not bad code.
Nothing can be assumed to be in sync for any data which is duplicated on multiple servers.
There is no application level software which can compensate for the distributed database problem.
@packetfire has posted an informix example on another thread which proports top solve the problem and does not. If the database system does not solve the problem, no application can solve it, and no database system can solve it.
The Internet has evolved without design or analysis, and more and more problems can be attributed to fundamental flaws. As we increase the size and loading, it is statistically more probable for more manifestations of fundamental design flaws.
Nail, meet hammer.
Where did I post an example? I do not remember doing so - if the example is incorrect or deficient, I should correct it or delete the failed attempt. But I seriously doubt that Amazon uses Informix, as Informix was bought by IBM in the 1990s, and the code merged into what we used to call “IBM DB-II”.