Hi Dhiren, we also had performance issues with Totara in Amazon's Cloud.

First recommendation: Establish one Memcached-Instance for Sessions and another one for caching. Especially that for caching had an huge impact on performance.

Second thing: Amazon's standard file system EFS is definitely not designed for use cases like Totara. It seems that Totara frequently accesses the file system, which takes way too much time when there are concurrent users in the system. If I remember correctly, we had performance issues as soon as there were 100 - 300 concurrent users. EFS seems to restrict the connections, so after a limit is reached the requests are queued. Solution for this was that our systemadmins somehow rebuild a NFS file system within the Amazon Cloud, because they don't offer NFS out of the box (Sorry, I don't know how they did this, I'm not an admin). Please be aware that NFS brings some disadvantages for Totara. The filelocking is not very reliable on NFS-systems (please correct me, if I'm wrong, but I read it in the moodle documentation). But we decided that we can live with that, as long as the system runs very much faster.

I hope this may help you.