SELECT 
  feature_id, 
  variant_id, 
  value, 
  value_int 
FROM 
  cscart_product_features_values 
WHERE 
  product_id = 262380 
  AND lang_code = 'en'

Query time 0.00140

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "633.60"
    },
    "table": {
      "table_name": "cscart_product_features_values",
      "access_type": "ref",
      "possible_keys": [
        "lang_code",
        "product_id",
        "idx_product_feature_variant_id"
      ],
      "key": "product_id",
      "used_key_parts": [
        "product_id"
      ],
      "key_length": "3",
      "ref": [
        "const"
      ],
      "rows_examined_per_scan": 528,
      "rows_produced_per_join": 26,
      "filtered": "4.94",
      "index_condition": "(`webmarco`.`cscart_product_features_values`.`lang_code` = 'en')",
      "cost_info": {
        "read_cost": "528.00",
        "eval_cost": "5.22",
        "prefix_cost": "633.60",
        "data_read_per_join": "20K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "value",
        "value_int",
        "lang_code"
      ]
    }
  }
}

Result

feature_id variant_id value value_int
611 8188
618 1541
621 36925
741 59394
817 61624
834 61621
835 59737
865 63611
897 62223
908 62634
909 62639
910 62671
913 62644
917 62651
920 62655
1149 67813