Hi,
I m developing POS system for fashion industry. It is multi branch enable, with off site branch operation. Which meant branch selling item without online link to hq database. Replication will be done at the end of day.

In my item table, it will link to colour grp and size grp which indicate that the particular item only have particular group of size such as X,M,L,XL but don have 6,7 size.

I am thinking that, if user change the item colour/size grp in hq, but the colour/size of item (which is not in new grp) was sold in other branch and replication is not done yet. Then, data in branch n hq will be inconsistent. How would you handle such offline concurrency problem?

Thank you