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 (1321) 
  AND a.status = 'A' 
ORDER BY 
  a.position, 
  a.variant_id

Query time 0.00064

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE a ref status,option_id,option_id_2 option_id 6 const,const 50 Using index condition; Using where; 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 modifier_type weight_modifier weight_modifier_type variant_name
23984 1321 507 0.000 A 0.000 A 54x78
23983 1321 509 0.000 A 0.000 A 54x98
23981 1321 609 0.000 A 0.000 A 65x98
23980 1321 611 0.000 A 0.000 A 65x118
23982 1321 614 0.000 A 0.000 A 65x140
23979 1321 709 0.000 A 0.000 A 74x98
23990 1321 711 0.000 A 0.000 A 74x118
23989 1321 714 0.000 A 0.000 A 74x140
23988 1321 911 0.000 A 0.000 A 94x118
23987 1321 914 0.000 A 0.000 A 94x140
23986 1321 1111 0.000 A 0.000 A 114x118
23985 1321 1114 0.000 A 0.000 A 114x140