A: Hi Gaspard,
40,000 API calls means that the number of calls to our HTTP REST APIs during one month must be below 40,000. Every time you GET the content of a page or SAVE a page you trigger an API call. If you use Static Site Generation you will trigger API calls just at build time (1 for each page every time you rebuild) and when you edit content, so it is very difficult to reach that limit.

500 MB of disc space is the space you have to save images (we count the space on our backend server, not the space on the CDN - which means you have 500 MB on our server + 500 MB on the global CDN).

50 GB of bandwidth means that the CDN bandwidth you have in one month must be less than 50 GB. For example, if you have 100 images of 50 KB each (5 MB total) you can have them downloaded 10.000 times each.

On the lifetime deals the limits are hard limits, so when you reach them you should upgrade to another plan. Really I think it's very unlikely that you will reach them unless you have a very high traffic website.