I am planning on doing some awfully heavy-handed updates to an old 1.4 store that is in production. The site is not really used for selling anything, but mostly used as an information library for each "product" being sold at a brick and mortar. There are Gift Cards being sold, but these are uncommon and they only sell once every handful of days or so, if this stopped working for a few days, it's not a big deal.
I would like to implement a data freeze on the site so that the database gets frozen for (most likely) a day or two while I migrate content/entities/etc over to another server instance. Putting the store in maintenance mode is not desirable, as I still want customers to be able to browse the site/product pages/etc, but I don't want anyone changing records during migration.
While I suspect some hard-editing of
index.php will be in order, I'd prefer to not have to edit any application files, and would rather freeze things at a server level.
With this in mind, what are some effective strategies for implementing a data freeze necessary for migrating entities?