I’m still only using it in a sandbox environment, but as far as I can tell the pricing is comparable to other card printing services. They are very responsive, if you reach out to them I’m sure they can give you a better answer.

Welcome! My first hex package was also a rest api wrapper (ex_force)

Here are some feedback/thoughts:

Dependency

• Although they are mostly swappable, recent packages chose jason instead of poison for json
• http client - I’m using tesla whenever possible since users can swap the http library easily.

Handwrite.Client

• Instead of "#{secret_key()}", you can make sure secret_key returns string value… which leads to the next point
• secret_key/0 calls System.get_env/1 on runtime - it may be okay for application (although not recommended), but for library, you should use application configuration (e.g. Application.get_env/3) (for global config) or pass that value down to the function.
  • For global configuration - check out sentry package
  • See configuration related sections at Library Guidelines as well

Code organization

• I found you made a module for each resource - such as Handwrite.Endpoint.Handwriting. There is no right answer, but I found it’s actually easier to read, use, and maintain the code I put the all things under one module if they’re at the similar level resources. See ExForce module source.
  • See also ExAws.S3 where the module have functions for each API call and introduce modules for high-level tasks, such as ExAws.S3.Upload (src)