Hi There,
I want to plan a migration using a backup, but likely some records will change during the time of downloading the backup and the planned migration,
How can I plan the migration in such a way that these changes are not lost?
Hello Jeroen_Vermunt and welcome to the forum 
Assuming that this is regarding a WordPress website that will be hosted in our WordPress hosting platform (instead of Application Hosting):
We cannot do database replication, so the recommended approach would be to intentionally temporarily freeze changes on the old host (such as by enabling a maintenance mode on the website).
You could freeze changes for the entire duration of the migration, or you could freeze changes at the very end and then perform a catchup operation, such as by re exporting the database at the old host and reimporting it at Kinsta at the end of the process. The second approach would minimize the time that the website needs to be frozen at the old host.
If you are requesting the Kinsta Migrations team to perform a migration for you, you can select an option in the migration request form to put your current website in maintenance mode. This involves installing a plugin (Maintenance) to block access to the website and prevent things like ecommerce transactions from taking place.
You can also leave notes at the end of the migration form to explain the situation better or make special requests. After the migration form is submitted, a conversation will be automatically opened with our Migrations team and they will correspond with you within the chat box in MyKinsta.