If I have a distributed database that is eventually consistent, what happens if I have something like a site where I’m selling products and I’m changing the price of an item?
If a product has price X and I update it to price Y, some versions of the database might still show price X. If a customer goes to check out, are there strategies to ensure they are actually getting the most up to date price, so they don’t get charged the incorrect value?
At some point, don’t I need to do some integrity checking of the data to ensure the most up to date value is being used?
We used to have a custom script which would track the replication lag, but that was a few years ago. Since then, we have moved to the heartbeat monitor provided by Percona Toolkit.
You may also want to consider adding the product they selected to their session, so if the price does change before they checkout, they won’t get sticker shock.