The same ruler,
turned on ourselves

Client names appear as industries, under confidentiality. The ten cells match rows 01–10 of the case ledger on the home page one for one.

1. 01

   Two people editing at once, neither one overwritten

   An order overwritten from another tab is not the user being careless. It is a data model missing a version column. We changed updates to optimistic locking with a version check: the conflict is stopped at the moment it happens, instead of being discovered later during reconciliation.

   Result0 order overwrite incidents
2. 02

   Syncing is not writing the whole payload back

   Product sync across tills used to write the entire payload back: machine A had just recorded a sale, machine B saved and wiped it out. After switching to per-record diff merging with deletion tombstones, the two machines each change their own fields and neither can flatten the other.

   ResultFull overwrite → per-record diff merge
3. 03

   Attack it yourself before it goes live

   We re-audited the coupon system from six angles: could the same coupon be spent twice, could stock be oversold, could an expiry date pick up sixteen extra hours once time zones were converted. All three turned out to be real, and all three were fixed before launch.

   ResultDouble-spend · oversell · timezone drift · fixed pre-launch

The three results come from rows 07, 01 and 01 of the case ledger on the home page.