[rich-tea]

You gained the ability to find the invoice. There is no need to have customer id in the invoice url. Just /invoice/invoice_id is enough.

[viraptor]

I meant a whole tree of methods. Sure, you can get specific invoices from `/invoice/id`, but you probably still want `/customer/id/invoices` or similar for searching through them. You could use extra parameters for `/invoice/...`, but I think often it's nicer to namespace that. (use case dependent)

[cs02rm0]

If an invoice id is unique across all customers. Which it probably should be, but other ids might reasonably not be.