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SELECT 
  a.*, 
  b.description 
FROM 
  cscart_currencies as a 
  LEFT JOIN cscart_currency_descriptions as b ON a.currency_id = b.currency_id 
  AND lang_code = 'tr' 
  LEFT JOIN cscart_storefronts_currencies AS storefronts_currencies ON storefronts_currencies.currency_id = a.currency_id 
WHERE 
  1 
  AND (
    storefronts_currencies.storefront_id IN (1) 
    OR storefronts_currencies.storefront_id IS NULL
  ) 
ORDER BY 
  a.position

Query time 0.00089

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	storefronts_currencies	system	PRIMARY,idx_storefront_id				0	const row not found
1	SIMPLE	a	ALL					4	Using filesort
1	SIMPLE	b	eq_ref	PRIMARY	PRIMARY	9	hobilifedt.a.currency_id,const	1	Using where

Result

currency_id	currency_code	after	symbol	coefficient	is_primary	position	decimals_separator	thousands_separator	decimals	status	modifier_rate	modifier_type	modifier_sign	auto_update	next_update	description
4	TRY	Y	TL	1.00000	Y	0	.	,	2	A	0.00000	A	A	N	0	Türk Lirası
1	USD	N	$	31.00000	N	10	.	,	2	A	31.00000	A	A	Y	1710363893	US Dollars
2	EUR	N	€	33.00000	N	20	.	,	2	A	33.00000	A	A	Y	1710363939	Euro
3	GBP	N	£	1.00000	N	30	.	,	2	A	0.00000	A	A	N	0	GB Pound