Sometimes this isn't possible.

I wrote an app that is basically a new UI for the Amazon products. It runs entirely on the client. The Amazon API simply didn't work in that setup.

Are you referring to the Product Advertising API?

Doesnt that require you to have a quota of affiliate sales to keep using it? I can’t find where they state this requirement but I remembered they were very sneaky about disclosing this. If you dont have any affiliate sales after X months, your API key will stop working.

Currently you have to be a member of their affiliate program to get API access. To become a full "member" you have to be a prospect who generates three referral sales (iirc) within a 30 day period. So once in you have the API, but getting in isn't as easy as filling out a form. From there you can get your API rate limits increased from the default 1x call per second up to 10 based on your prior 30 day affiliate sales.

Last I looked that limit was per IP address.

Man, looks great. I also build something similar in node.js. I implement everything what documentation said (complete implementation). ICYMI:

https://github.com/Ribhnux/piranhax

The API comes with a TOS that severely restricts what you can do with the data.