aws ELB vs. ALB Review: Performance,Resiliancy

Question

It has been almost a year since aws deployed the ALB.
There seems to be little to none technical comparison between the classic LB and the ALB.
The only thing that my research yielded is: aws forum question

While the above implies that ALB is not reliable it is only one source.
I am interested in knowing the experience of people who did the switch between ELB and ALB, mainly in regards to latency, resilience, HA.
It seems to me that Layer4 balancing is more robust than Layer7 and therefore the general performance would be better.

Answer 1

I would like to provide my experience here, but I am not going into very detail. Basically my company has over 200k devices on the field actively connecting our backend via websocket. We were using ELB in front our servers and it was working quite well, all the connections were quite stable. We tried to switch ELB to ALB before, but the result wasn't really good and we switched back.

The main problem we found the connections were dropped suddenly (with a pattern like every 15 hrs?). Please check the graph of number of connections I captured from the monitoring system:

As you can see there are some dips in the graph which showing the connections have be dropped. I keep the same server setup, only factor I have changed is from ELB to ALB and got this result.