Hi David, It would be useful if you could provide your measurements and the way you arrived at such results. A quick test doesn't seem to support your findings: https://3v4l.org/v5m9f#v8.1.8
There are already a number of optimizations in array_merge. It might depend on the actual test data that you used. Maybe a specific path needs to be optimized. Please provide some more details. Regards, Kamil
