Accumulated Magento 2 orders will increase the save() time at the DB linearly.
Saving an Order either from Transaction, Editing, or editing a field related to an order such as addresses, are showing a decay of increased time from the DB when you save the record.
Transaction from new will take under 4 seconds including the load of the success page, and now with thousands of records later, the save() is taking over 15seconds to return, making the transaction time close to 20secs.
We have proved it is the transaction records in the DB causing this by removing them, and getting the 4 sec experience back. What is causing this delay? and as more transactions come in, the delay keeps increasing. Help!? We expect over 3k-4k transactions a week, at this rate it impacts the checkout by 1sec/day longer...
Additionally Magento 1 orders that were transferred have no effect on this issue it is just Magento 2 orders.