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SELECT 
  cscart_languages.* 
FROM 
  cscart_languages 
  LEFT JOIN cscart_storefronts_languages AS storefronts_languages ON storefronts_languages.language_id = cscart_languages.lang_id 
WHERE 
  1 
  AND cscart_languages.status = 'A' 
  AND (
    storefronts_languages.storefront_id = 1 
    OR storefronts_languages.storefront_id IS NULL
  )

Query time 0.00012

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_languages	system					1
1	SIMPLE	storefronts_languages	system	PRIMARY,idx_storefront_id				0	const row not found

Result

lang_id	lang_code	name	status	country_code
1	tr	Türkçe	A	TR