ArangoDB’s Foxx allows you to easily build an API to access your data sources. But now this API is either public or restricted to users having an account, but those still get unlimited access.
In many use cases you do not want to expose your data in this fashion, but you want to expose it with a more controllable access pattern and want to restrict the requests one user could issue in a certain time period. Popular examples for these API restrictions are Twitter or Facebook. This allows you to offer all of your data but only in limited chunks, and then possibly charge your customers to increase the chunk limit they can request.
All this is done via API keys, which are bound to a user and has become a common pattern to monetize the data you have collected. More info