@yewnity 

I am consistently getting 200-250Mbps on Satellite M5 when it is connected to Main Deco by WiFi backhaul. My Satellite and Main are on different floors of the house, separated by wooden floor.

I would recommend re-running speedtests with following setup:

1. Deco mesh in AP mode.

2. Satellite Deco #2 is turned off.

3. 2.4GHz in Deco WiFi settings turned off, only 5GHz left.

4. Use smartphone to run speed test.

5. Verify smartphone is connected to Satellite Deco, not to Main Deco, before running speed test. 

6. Use more than one speed testing web site or app: fast.com, speedtest.net, and so on.

Also, check what does Signal Source show in Satellite Deco, it'll tell you if WiFi signal quality between Satellite and Main Decos is good or not. Example:

Low WiFi backhaul signal quality between Main and Satellite could impact internet speed of mobile device connected to Satellite Deco dramatically.

@Alexandre. 

Thanks for your input. Have rerun the tests based on the setup.

Results were marginally better with 60Mbps on Speedtest, 34Mbps on Fast.com

I have then switched back to Router mode and speeds improved to 81.67 Mbps on Speedtest, 47Mbps on Fast.com

Signal source is the same as the screenshot which you have provided with 2/3 bars. I have move the Satellite Deco closest to the main Deco as possible on the second floor, almost above the Main Deco.

I wish I could achieve the speeds you are achieving with your Satellite. Until then I won't be giving up so easily.

@yewnity 

You can try Deco Lab/WiFi Assistant in Deco app, to see what sort of WiFi interference you have around Satellite Deco. Mine reports Low. 

I would suggest running WiFi interference test multiple times, its results could fluctuate.

Not much you can do if it is medium to high, but at least you'll know possible cause for slow speed especially if interference is reported high all the time.

@yewnity Got a 1GB line, Deco is getting 800+ Up & Down, connected via LAN sweet i get the same speed. I go over WiFi i get 400mb, i thought may be my device is going over 2Ghz so i turn that option off in app result - still 400mb. It getting throttled over WiFi. I had support online for 1hr didn't help. 

@TP-Link 

My best speedtest result with wired M5 in AP mode on 5GHz in almost ideal testing conditions is 460Mbps. I thought this is the price we are paying for form factor, sacrificing speed for the compact size of the Deco M5.

The best I am getting from M9 Plus in same testing conditions is 630Mbps.

Yet, if TP-Link Engineers think M5 can do better, please let us know what top speeds to expect from M5.

Thanks.

@Alexandre. 

Mine reports low as well in multiple tests. It is weird that speeds would be affected when the interference is at low.