SELECT 
  a.variant_id, 
  a.position, 
  a.modifier, 
  a.modifier_type, 
  a.weight_modifier, 
  a.weight_modifier_type, 
  a.status, 
  a.yml2_variant, 
  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, 
  b.variant_name 
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 = 'ru' 
  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 = 748 
ORDER BY 
  a.position

Query time 0.00041

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "4.05"
    },
    "ordering_operation": {
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "shared_option_variants",
            "access_type": "system",
            "possible_keys": [
              "PRIMARY",
              "company_id"
            ],
            "rows_examined_per_scan": 0,
            "rows_produced_per_join": 1,
            "filtered": "0.00",
            "const_row_not_found": true,
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.10",
              "prefix_cost": "0.00",
              "data_read_per_join": "24"
            },
            "used_columns": [
              "variant_id",
              "company_id",
              "modifier",
              "modifier_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "a",
            "access_type": "ref",
            "possible_keys": [
              "option_id",
              "option_id_2"
            ],
            "key": "option_id",
            "used_key_parts": [
              "option_id"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 9,
            "rows_produced_per_join": 9,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "2.25",
              "eval_cost": "0.90",
              "prefix_cost": "3.15",
              "data_read_per_join": "10K"
            },
            "used_columns": [
              "variant_id",
              "option_id",
              "position",
              "modifier",
              "modifier_type",
              "weight_modifier",
              "weight_modifier_type",
              "status",
              "yml2_variant"
            ]
          }
        },
        {
          "table": {
            "table_name": "b",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "variant_id",
              "lang_code"
            ],
            "key_length": "9",
            "ref": [
              "primapearl_r_new.a.variant_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 9,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.00",
              "eval_cost": "0.90",
              "prefix_cost": "4.05",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "variant_id",
              "lang_code",
              "variant_name"
            ]
          }
        }
      ]
    }
  }
}