EFS is intolerably slow and keeping your php files on it is a bad idea. It's a little more complex but using packagist to install everyy except locally and the

EFS is intolerably slow and keeping your php files on it is a bad idea. It's a little more complex but using packagist to install everyy except locally and then put wp-content/uploads/ on EFS works okay. fs-cache/cachefilesd helps.