哪种缓存方法是Node / Mongo / NginX最快/最轻的？

I've been tasked to work on a project for a client that has a site which he is estimating will receive 1-2M hits per day. He has an existing database of 58M users that need to get seeded on a per-registration basis for the new brand. Most of the site's content is served up from external API supplied data with most of the data stored on our Mongo setup being profile information and saved API parameters. I've been tasked to work on a project for a cli