RapidAPI. You can consume multiple API's from one account and as a developer it's a good way to monetize an API if there isn't too much competition in your niche. Not sure what you mean by firewalling but RapidAPI does authenticate their requests to your endpoint so as a developer you can do access control in this way.
Re:What’s your API’s “Time To 200”?
by sagarpatil on Saturday May 22, 2021 @10:28PM
(#27251962)
Yep. Can vouch for RapidAPI.
Something that would consolidate account, tokens, billing, tracking, firewalling etc of an API?
Somewhere where one could plug their api and monetize it easily?