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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 = 'de' 
  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 = 1 
WHERE 
  a.option_id IN (337, 686, 336, 687) 
  AND a.status = 'A' 
ORDER BY 
  a.position, 
  a.variant_id

Query time 0.00239

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		16	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
15689	687	20	A	A	20 mm
15690	687	30	A	A	30 mm
15691	687	40	A	A	40 mm
7668	336	50	A	A	50 mm
15692	687	50	A	A	50 mm
19507	686	50	A	A	50 mm
7677	337	80	A	A	80 mm
7670	336	100	A	A	100 mm
7678	337	100	A	A	100 mm
15665	686	100	A	A	100 mm
7671	336	120	A	A	120 mm
7679	337	120	A	A	120 mm
15666	686	120	A	A	120 mm
7680	337	140	A	A	140 mm
15667	686	140	A	A	140 mm
7673	336	150	A	A	150 mm
7681	337	150	A	A	150 mm
15668	686	150	A	A	150 mm
7682	337	160	A	A	160 mm
15669	686	160	A	A	160 mm
7683	337	180	A	A	180 mm
15670	686	180	A	A	180 mm
7676	336	200	A	A	200 mm
7684	337	200	A	A	200 mm
15671	686	200	A	A	200 mm
11878	336	250	A	A	250 mm
11877	336	300	A	A	300 mm