I was updating my symfony plugins using composer and I received the following error in ssh:
Loading composer repositories with package information
Updating dependencies (including require-dev)
Killed
My research founded that it's because the ec2 instance does not have enough ram to perform such an update.
What you can do is to do a "composer.phar update" in a local machine. This would produce a composer.lock file.
Upload this .lock file to production, and run "composer.phar install" instead.
