We have performed load testing using JMeter for 100 users. For the first few requests everything works fine but after sometime Gateway timeout error is encountered.Please refer to screenshot: http://imageshack.com/i/pnnrBje4p
In the beginning, same APIs run successfully but later the very same APIs return this error (504 Gateway Timeout Error).
We have configured mattermost with AWS server .
AWS server details:
Web Server Instance
Instance Size: C3 2X large
RDS Server Instance
Hard to tell what your problem is without some logs from the Mattermost server. Also are you using a machine running Nginx as we suggest or are you using another proxy like ELB?
For our next release (3.5 November 16) we are doing a big push on performance. If your considering using Mattermost at a scale above 10000 users I would evaluate our current master build. You can find that here: https://releases.mattermost.com/mattermost-platform/master/mattermost-enterprise-linux-amd64.tar.gz
We are currently working on a document to help people setup Mattermost at large scale. Some suggestions from that document:
Modify your /etc/init/mattermost.conf to be:
start on runlevel 
stop on runlevel 
limit nofile 50000 50000
Modify your ulimits on your proxy and Mattermost machines. (by editing /etc/security/limits.conf)
ulimit -n 65536 65536
ulimit -u 8192 8192