Alibaba Cloud SLB can distribute user requests to backend ECS instances, but these ECS instances do not have to have the same specification (CPU, Memory). SLB virtualizes the added group of ECS instances in the same region into an application pool, and you can manage backend servers through either the default server group, a primary server group, or VServer groups. You can add ECS instances of different specifications to the same server group or VServer group according to your needs. SLB supports weighted round-robin (WRR) and weighted least connections (WLC) algorithms to balance the load among backend servers with different weights. References:
* SLB overview - Alibaba Cloud
* Backend server overview - Alibaba Cloud
* What is Server Load Balancer and How It Works - Alibaba Cloud
* Server Load Balancer - Alibaba Cloud
* Alibaba Server Load Balancer (SLB) Course - Cloud Academy