Get Basemaps without exposing API Key

Question

I'm building an aplication using leaflet JS for a company and i want to use the esri basemaps URL to get the tiles for the map. By following the tutorials I got a solution where I created an API key that I use to get this information, but it exposes the API Key in the js. I did not like this approach so I built an API endpoint that act as a middleware and joins the esri basemaps URL with the API key token. However this approach proves enificient since some HTTP get request take several seconds to return. 
I am using plain HTML and js with the library Leaflet, I may use the Esri-leaflet integration library but the problem persist.

Am I missing something, or is there another approach to solve this problem?

LightmobieLDA · Answer

Thank you very much for your feedback and help @Edvinas_S  and @Noah-Sager. I will follow your advise.

Noah Sager · Answer

Unfortunately, I don't know much about the legal aspects. I would take @Edvinas_S's recommendation and account your account manager with Esri. We do have this page on licensing and attribution for the JS SDK: https://developers.arcgis.com/javascript/latest/licensing/

Edvinas_S · Answer

If a service does not require any kind of authentication (like a log-in or an API key), that means it doesn't use your credits and it doesn't know who is sending requests. Weather or not you can use these free-of-charge services in a commercial product depends on the license. My guess is that it would be ok to use esri default basemaps. You should contact Esri support to make sure.