@zcx 

The 6 rule is more for Deco devices connected wirelessly, once you pass 6 it's a case of greatly diminishing returns due to the traffic going over the air. 

However if you are running these via LAN connections, you are likely not going to have this issue.   Ive run 8 decos before in AP mode over LAN without issue.

  @Philbert

Thank you for your reply!

Noted, so theoritically is true, there is no limit if deco connected via ethernet backhaul.

Am planning to buy another 6 deco then, can we connect more than 10 deco on a single network?

another 6 deco will connect with ethernet backhaul too..

  @zcx 

If you are going to connect them via backhaul ethernet, I cant see you having an issue with this, however i have not personally used that many before.  

Usually when I would pass that many APs I would look towards an Omada solution.

In theory there is no reason this wont work

  @zcx 

This TP-Link FAQ article may help, too: How many Deco units can I add to my Deco mesh network?

If you run Deco mesh in AP mode, my recommendation would be not to connect all Satellite Deco through Main Deco. Meaning, don't do this:

Do this instead:

Thank you guys for your reply!

Never experience about omada and also about the price kinda expensive here,

This deco for guest house something like that, on 1 building there is 80-90 people renting..

My topology in my businesss building network.

2 ISP - Mikrotik x86_64 - 16 Gigaport Port Switch - Deco, TP Link Router and Other mixed brand.

My plan to eliminate all the dead zone spot and make single wifi network seamlessly :)

  @zcx 

Honestly, for what you are looking to achieve the Omada would be the better option for you and give you a LOT more control.   Price wise, it will be a tad more expensive but far superior overall.

Just off the head here, this is what you would need to get a minimum setup, not sure where you are based but this is the rough euro price

1 ER605 Router  ~€60

1 OC200 Controller  ~€60

however many EAP610  ~€120 each

Just use your existing switch (POE?)

The advantage of this is you can bond both ISP connections into one super connection to share and offer redundancy.  The controller allows you to setup GUEST portals, multiple SSIDs and PPSK encryption, amongst a dozen other things that Deco isnt designed for.  

The EAP610 would handle more capacity and be faster than the Deco.. different grade of hardware

The Omada would be a much better solution for 90+ users.   You would honestly be stretching Deco to the Limits.

  @Philbert 

thank you for replying and the suggestion. I will consider about it.

Because the price is kinda affordable with deco x20 instead of buying omada.

buying 1 omada eap610 can get almost 2 deco x20

Almost all feature on deco x20 are disabaled when am on access point mode.

The one that im looking for is the mesh, cloud and user friendly interface, because mostly am not in the area.

for all traffic are being handle with Mikrotik.

im using 2 isp, isp A 250 and isp B 200, am not using the load balancing stuff because mostly they are not stable. My load balancing stuff only turn on for speedtest only.

right now am using separate traffic, so for heavy load traffic such as youtube netflix tiktok instagram twitter and some other streaming platforms on my country, am using ISP B, else traffic to ISP A.

all are good at the moment, to be honest i dont have experience how many client that deco can handle on access point mode, the marketing stuff said 150 devices but i think thats if you are using router mode, i believe if you are on access point mode, devices can handle more than that.

Cause right now usually they connect around 60-80 devices on deco, on other mixed brand router around 50-70 devices in total, traffic around 200-300 mbps on peak hour, else stable from 50-100 mbps.

  @zcx 

While ive never personally pushed this to the max to test it, going by most accepted testing and knowledge of the technologies.. generally a single AP is good for around 50 connections max, that might jump to 80 or 90 if its an HD (High Density) model designed for mass area traffic.. personally always went with 40 clients MAX per AP

The problem isnt the AP as such, more the fundamentals of how the data flows over the air.. without going into too much detail the more clients you have the longer it takes for each client to get a period of air to transmit... its an exponential problem.    When AP manufacturers claim 150 devices, YES you can connect 150 devices at once.. just dont expect to do much surfing, if they are just connected and idle its likely do-able, but if you try to use it NOPE .  General rule of thumb.. 40 per AP

If you are running AP mode on Deco, then yeah you are fine with 6-8 Deco to cover 150 connections. 

Also remember that 5ghz connections are much more functional vs 2.4ghz.   You will get 35-40 on 5ghz, 8-10 at most on 2.4ghz, simply due to the congested airspace.