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What is minimum memory (RAM) requirements to APEX Listener 1.1.4 running 100 concurrent users?
For 100 concurrent users you should be deploying ApexListener in a J2EE container as has been advised in the documentation.
The RAM and CPU requirement will be determined by the J2EE container you decide to use. ApexListener is a small servlet and its resource requirement is miniscule compared to that of the J2EE container.
in addition to the fact that you shouldn't run an APEX Listener scenario with 100 concurrent users in Standalone Mode, memory requirements will also depend on your application. And I'm not sure it's just a question of memory if you actually have 100 concurrent users, but you'll have to think about CPUs, especially on your backend.
I'd always recommend a fitted load test for your scenario to see where your bottlenecks are.
I've been looking for data about cpu and memory usage by APEX Listener but nothing found. The system/platforms department asks us for consumption of memory and cpu data to estimate the impact on other applications in the WebLogic server. I understand that this is hard to estimate because it depends on the type of application. Could anyone give some information for memory & cpu usage of APEX Listener for about 25, 50 or 100 concurrent users doing requests on an apex application?