4×× Client Error
404 Not Found
The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.
A 404 status code does not indicate whether this lack of representation is temporary or permanent; the 410 Gone status code is preferred over 404 if the origin server knows, presumably through some configurable means, that the condition is likely to be permanent.
A 404 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls1.
404 Code References
Rails HTTP Status Symbol
Go HTTP Status Constant
Symfony HTTP Status Constant
Python2 HTTP Status Constant
Python3+ HTTP Status Constant
Python3.5+ HTTP Status Constant