Pretty much everything the OP mentions is reasonably basic &quot;core IT&quot; concepts. Depending on what he means by &quot;intermediate sql&quot; that might or might not fit into that category. 
I don&#x27;t think it&#x27;s unreasonable to expect a &quot;full stack&quot; dev to have at least a basic understanding of things like DB indexing, singletons, http get vs post. 
Where I would agree with you is to become proficient with these concepts it does involve spending some time in the industry  so the age thing might be the factor here as well. 
Personally I would strongly prefer these types of questions to the &quot;recent CS graduate&quot; type questions some companies are notorious for and not just because I can answer these :)