Hi @Marcel_Ueno
When importing using the ReplaceAll mode, the keys that are currently within the table itself, but not in the csv file will be deleted first. Then, the csv gets processed where those records are inserted into the database. If the key is already within the table, it is just updated. There shouldn't be a window where that key gets deleted. However, this is an async process, so the time it gets updated depends on which row it is within the csv. When using Append mode, the first step is skipped, so there are no deletes. The inserts/updates to existing rows happen the same way.
Row lookups should be available while the import is processing, but there may be race conditions where the lookup may still return old data while the csv is being processed.
It should be no different than if someone was manually updating the row in AdminUI while a flow was actively looking up the row.