Why
We checked availability by hand. Two pieces were double-booked (as reported to us) because neither store could see the other's bookings.
What I built
- $0 hold orders, in the store's own booking format, block dates on the other calendar.
- The partner's public calendar is mirrored the other way.
- It polls every 2 minutes from my own machine.
Hardest problems
- The documentation was wrong; the format copied from real checkouts worked.
- The partner's orders carried no dates, so the sync mirrors their public calendar.
- Every fix shipped with a regression test, taking the suite from 60 to 459.
Results
- 6 of 7 reconciliation checks came back clean; the seventh caught 2 missed bookings, since fixed.