Import large number of entries every day - 1 million
You could write a service method that reads the import file and divides it into chunks, then it could dispatch a queue job for each chunk which does the actual entry creation/update. This way you could scale the resources and amount of queue workers available to work through the queue and even Play with the chunk size.
In the queue job you might want to implement proper exception handling to keep track of unsuccessful entry operations to handle them somehow.