What is the maximum number of inserts we can achieve with MySQL 5.7 and MySQL 8.0 assuming that the supporting hardware is optimal.
It depends on your frame of reference. How much data can you put into a table/schema? Inserts per second?
An InnoDB table can have a maximum of 1017 columns with a maximum of 64 secondary indexes. With 64k pages you can have a maximum of 256tb size tables. And you can always have multiple tables so the biggest amount of data is dependent more on your hardware and operating costs.
And do not forget the old MySQL protocol lets you send a maximum of roughly 1GB at a time.
So what do you mean by maximum inserts?