As a software developer I insisted on buying a 4K Monitor which used to work with my previous MBP 2017 quite ok.The Retina MBP Late 2015 has output that lags quite a bit when I use a scaled resolution.
The output is only OK if i try the 4k or 1080p resolutions which are not very optimized for reading things on the screen.
Is there any way to optimize this? The lagging performance can be seen when I do something with Java VM especially Android Studio.
UPDATE
I connected my mac book over mini display to display port since HDMI does not support 60hz. Lag means when you scroll the code editor in Android studio, it is not very fluent.If i type something there is a small time gap till i see the letters appear on the screen.
Best Answer
Scaling is your culprit. Anything different than 1080p or 4K is going to tax the GPU and cause lag. It's unfortunate. I think a solution which costs a lot more money would be to purchase a 5K monitor then run it at 1440p (the only acceptable resolution imho) This would be the default resolution since it's exactly half of 5K. 1080p is exactly half of 4K which is why the GPU doesn't struggle on a 4k monitor when run at that resolution. Of course 4k at it's natural resolution is far too tiny to be useable which I'm sure you found out. So 1080p and 4k are just not useable for a 27" monitor. Purchasing a blurry 1440p monitor or a 5K monitor run at retina 1440p are the only options to get a lag free experience imho on a 27" external display paired with a MacBook Pro.