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SELECT 
  a.variant_id, 
  a.option_id, 
  a.position, 
  a.modifier, 
  a.modifier_type, 
  a.weight_modifier, 
  a.weight_modifier_type, 
  b.variant_name, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier, 
    a.modifier
  ) as modifier, 
  IF(
    shared_option_variants.variant_id IS NOT NULL, 
    shared_option_variants.modifier_type, 
    a.modifier_type
  ) as modifier_type 
FROM 
  cscart_product_option_variants as a 
  LEFT JOIN cscart_product_option_variants_descriptions as b ON a.variant_id = b.variant_id 
  AND b.lang_code = 'en' 
  LEFT JOIN cscart_ult_product_option_variants shared_option_variants ON shared_option_variants.variant_id = a.variant_id 
  AND shared_option_variants.company_id = 2 
WHERE 
  a.option_id IN (338, 1290) 
  AND a.status = 'A' 
ORDER BY 
  a.position, 
  a.variant_id

Query time 0.00055

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	a	range	status,option_id,option_id_2	option_id	6		24	Using index condition; Using filesort
1	SIMPLE	b	eq_ref	PRIMARY	PRIMARY	9	mahm3t_cs443.a.variant_id,const	1	Using where
1	SIMPLE	shared_option_variants	eq_ref	PRIMARY,company_id	PRIMARY	7	mahm3t_cs443.a.variant_id,const	1

Result

variant_id	option_id	position	modifier_type	weight_modifier_type	variant_name
7685	338	9	A	A	9 mm
7687	338	12	A	A	12 mm
23644	1290	12	A	A	12 mm
7690	338	15	A	A	15 mm
23645	1290	15	A	A	15 mm
7689	338	18	A	A	18 mm
23646	1290	18	A	A	18 mm
7688	338	22	A	A	22 mm
23647	1290	22	A	A	22 mm
7686	338	25	A	A	25 mm
23648	1290	25	A	A	25 mm