How-To: Integrate Amazon FBA into Shopify
Edit: I now have a Multi-Channel Fulfillment calculator that is free to download at: https://tools.paulrecchia.com/mcf-calc
Amazon FBA is the greatest logistics provider in the world.
If you're selling on Shopify, and you are running out of warehouse space, consider letting Amazon handle your logistics.
Note: As stated in the video, I went and figured out what happens if your shipping types are not set up just how they appear on Amazon (Standard Shipping, Expedited Shipping, Priority Shipping). If a user selects a shipping method that does not match to one of Amazon's methods, you will get an error when Shopify tries to fulfill the order.
More details here: https://help.shopify.com/manual/shipping/rates-and-methods/fulfillment-services# set-amazon-rates