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 (998) 
  AND a.status = 'A' 
ORDER BY 
  a.position, 
  a.variant_id

Query time 0.00043

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 4 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
19624 998 120 0.000 A 0.000 A C2A | 55x78 cm
19626 998 140 0.000 A 0.000 A C4A | 55x98 cm
19627 998 360 0.000 A 0.000 A F6A | 66x118 cm
19628 998 540 0.000 A 0.000 A M4A | 78x98 cm
19629 998 560 0.000 A 0.000 A M6A | 78x118 cm
19630 998 580 0.000 A 0.000 A M8A | 78x140 cm
19625 998 760 0.000 A 0.000 A S6A | 114x118 cm