For PVM clients with a previous version (1.2) wishing to upgrade to 1.3 (latest), there may be chances that after the upgrade or migration, your system is unusable. This may have happened especially if the instance capacity is low.
We advise clients to look into /var/log/php-fpm/www-error.log to find the specific cause of the issue. In the error log, if you see a lot of “memory allocate error”, this is an indication that the memory is not sufficient.
So in case of t1.micro instance (600 MB), you might want to consider a higher instance than this, such as m1.small or t2.micro. Although these two have higher memory than t1.micro, m1.small is PVM, while t2.micro is HVM.
If you currently use PVM and wish to use HVM, it is necessary to create a new HVM instance before migrating from PVM to HVM.