I am running CF 2016 and recently launched a site with a ton of traffic. I see that there are a lot of active sessions. I have set the application session timeout to 5 minutes but when the traffic gets high, the server stops slows down. I am pretty certain that the issue is a tuning issue but I don't know enough about tuning to start testing a solution.
CF2016 update 10 offers support for Java 11. Perhaps you will see tune improvement by changing the JVM from 8 which CF2016 is likely configured for to 11.
To give you suggestions on performance tuning, it would help if we knew the following:
Operating System (version, bits)
ColdFusion Edition (Standard, Enterprise, 32 or 64bit)
Java version that ColdFusion uses
the JVM settings in ColdFusion