Nginx Connnection Timeout

Hello,

Background
I have a application that will connect into 2 nginx proxy then connect into AWS ElastiCache Redis.
The nginx proxy is configured to be like a TCP load balancer. The nginx will listen on the port 80 then push the request to the next nginx then finally into redis.

Issue
I am having timeout connection issue every 10mins. I have increased to 1hour but the timeout still persist. I am not sure of what configuration to resolve this timeout issue. Is there any connection limit that free version of nginx can support as compared to nginx plus ?

Version: 1.17.5 (Using the free version)
I deployed nginx using the Docker file on docker hub.


Thank you