hi all sifoo, i having problem with my macbook pro when editing photo using LR,
my fren told me i have to upgrade my RAM as the orginial 8GB is not enough


Question :
1) may i know where to buy RAM for MAcbook ?

2) my mac model is 2015 (retina 13") does it support 2 x RAM ?

3) 1 x 16 GB RAM & 2 x 8GB RAM (which 1 is better performance)

thanks for advice

2015 MacBook Pro cannot upgrade RAM. Unless you want to change your motherboard. RAM is soldered/stuck.

omg, really no other solutions ?

Yep, it's soldered, there's no way to change the RAM.

Lightroom hmm, my experience with Lightroom is, even with some fairly good hardware (16GB RAM, i7) it still performs...sluggish. I have another 4GB RAM laptop that performs similarly to my 16GB desktop in Lightroom.

It's well known that Lightroom is not really well optimised (no proper multi-threading, unresponsive/stuttering UI). See some complaints here.
What affect lightroom performance the most is the storage. But since you're using Macbook 2015 it has SSD already unless you put every photo in external harddisk.

thanks
my macbook have plenty of spaces, i only install few apps including LR
i dun keep big file in my macbook SSD. my problem is that when the macbook processor is hot, the LR become very very slow, sometimes even no response when i play with slider adjustment

Then I afraid it's more of CPU issue, because CPU will throttle (slow) itself when it get too hot to protect itself from overheating. Check your CPU temperature (can use smcFanControl to check), if it reaches >90 celcius all the time then you might need to find someone to help you clean your macbook or replace thermal paste.

If temperature is ok, then perhaps macbook processing speed is not enough for your work. Probably what suits you more is a full desktop (better processor, ram, etc) since your work on LR sounds pretty heavy. I don't use much LR on my laptop and macbook, only for minor editing, and on laptop/macbook I use only SmartPreview (this helps a lot!) instead of original source. Most heavy editing and work still back to desktop though.