When it comes to the use of micro-services and APIs. It appears pretty common for a few key response codes to be used. However, if you look at the IANA Status Code Registry of defined codes, there a number of other very useful codes that can help convey issues clearly, without compromising security.
The IANA list, references the relevant IETF RFCs, but I’ve taken this a step further and obtained the relevant deep hyperlinks to the code explanations. In addition to that, I’ve also highlighted some response codes, that perhaps benefit from a closer look, or considered with caution.