Depending on your use case, you'll probably come across one of these errors at some point while using composer.
composer update (out)PHP Fatal error: Allowed memory size of XXXXXX bytes exhausted
Or the wonderfully informative.
composer update (out)Killed
You can go and edit your
php.ini, start composer with
php -d memory_limit=-1 composer [command], or go with the nice and easy way for one off updates.
COMPOSER_MEMORY_LIMIT=-1 composer update (out)[composer runs, assuming you have enough RAM]