> Responses to POST requests are only cacheable when they include > explicit freshness information (see Section 4.2.1 of [RFC7234]). > However, POST caching is not widely implemented. For cases where an > origin server wishes the client to be able to cache the result of a > POST in a way that can be reused by a later GET, the origin server > MAY send a 200 (OK) response containing the result and a > Content-Location header field that has the same value as the POST's > effective request URI (Section 3.1.4.2).

@malcolmsparks: is that the reason that yada sends a 200 instead of 201 after successful creation?

https://tools.ietf.org/html/rfc7231#section-4.3.3