Creating the MediaWiki parser is an expensive operation as it is a heavy class with many dependencies (Some infos at T236811).
So the parser creation should be avoided during service creation and should be done when needed.
This includes the call to MediaWikiServices::getParser() from service wiring files like core's includes/ServiceWiring.php.
This includes the use of Parser in object specs, for example for api modules or special pages, but also other usages of specs to ObjectFactory.
This includes calls to parser factory in construtor of service classes
Always use spec for ParserFactory and store that instance, create the parser when needed via ParserFactory::create, ParserFactory::getMainInstance ParserFactory::getInstance
Searches with false positives: