Under what conditions is a response to POST cacheable?
Only when it includes explicit freshness information and a Content-Location field equal to the POST's target URI✓Правильный ответ
Never; POST responses are excluded from caching entirely
Whenever the response carries an ETag, since that permits later validation
Whenever the response carries Cache-Control: public, regardless of other fields
Объяснение
Both conditions are required together, and the resulting cached entry can then satisfy a later GET or HEAD. A subsequent POST can never be served from that entry, because POST is potentially unsafe.