SELECT 
  pf.feature_id, 
  pf.company_id, 
  pf.feature_type, 
  pf.parent_id, 
  pf.display_on_product, 
  pf.display_on_catalog, 
  pf.display_on_header, 
  pf.categories_path, 
  pf.status, 
  pf.comparison, 
  pf.position, 
  pf.purpose, 
  pf.feature_style, 
  pf.filter_style, 
  pf.feature_code, 
  pfd.description, 
  pfd.lang_code, 
  pfd.prefix, 
  pfd.suffix, 
  pfd.full_description, 
  pfv.value, 
  pfv.variant_id, 
  pfv.value_int, 
  pfv.product_id 
FROM 
  cscart_product_features_values AS pfv 
  LEFT JOIN cscart_product_features AS pf ON pfv.feature_id = pf.feature_id 
  LEFT JOIN cscart_product_features_descriptions AS pfd ON pfd.feature_id = pf.feature_id 
  AND pfd.lang_code = 'en' 
WHERE 
  1 = 1 
  AND pfv.product_id IN (
    7496, 7497, 7500, 7501, 7506, 7507, 7528, 
    7529, 5219, 1516, 5217, 5216, 3728, 
    5215, 5218, 1513, 1512, 1514, 1511, 
    1515, 5231, 5229, 514, 3730, 5228, 5230, 
    1530, 1527, 3675, 1528, 1526, 1529, 
    5214, 5212, 5211, 3727, 5210, 5213, 
    1510, 1507, 1506, 1508, 1505, 1509, 
    5236, 5234, 5233, 3731, 5232, 5235, 
    1536, 1533, 1532, 1534, 1531, 1535
  ) 
  AND pfv.lang_code = 'en' 
  AND pf.feature_code IN ('Brand', 'ISBN', 'GTIN', 'MPN')

Query time 0.00856

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1804.37"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "lang_code",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "idx_product_feature_variant_id",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 2716,
          "rows_produced_per_join": 1159,
          "filtered": "42.69",
          "index_condition": "((`gaseus`.`pfv`.`product_id` in (7496,7497,7500,7501,7506,7507,7528,7529,5219,1516,5217,5216,3728,5215,5218,1513,1512,1514,1511,1515,5231,5229,514,3730,5228,5230,1530,1527,3675,1528,1526,1529,5214,5212,5211,3727,5210,5213,1510,1507,1506,1508,1505,1509,5236,5234,5233,3731,5232,5235,1536,1533,1532,1534,1531,1535)) and (`gaseus`.`pfv`.`lang_code` = 'en'))",
          "cost_info": {
            "read_cost": "1120.26",
            "eval_cost": "115.95",
            "prefix_cost": "1236.21",
            "data_read_per_join": "896K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id",
            "value",
            "value_int",
            "lang_code"
          ]
        }
      },
      {
        "table": {
          "table_name": "pf",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id"
          ],
          "key_length": "3",
          "ref": [
            "gaseus.pfv.feature_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 463,
          "filtered": "40.00",
          "cost_info": {
            "read_cost": "289.88",
            "eval_cost": "46.38",
            "prefix_cost": "1642.04",
            "data_read_per_join": "547K"
          },
          "used_columns": [
            "feature_id",
            "feature_code",
            "company_id",
            "purpose",
            "feature_style",
            "filter_style",
            "feature_type",
            "categories_path",
            "parent_id",
            "display_on_product",
            "display_on_catalog",
            "display_on_header",
            "status",
            "position",
            "comparison"
          ],
          "attached_condition": "(`gaseus`.`pf`.`feature_code` in ('Brand','ISBN','GTIN','MPN'))"
        }
      },
      {
        "table": {
          "table_name": "pfd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "gaseus.pfv.feature_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 463,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "115.95",
            "eval_cost": "46.38",
            "prefix_cost": "1804.37",
            "data_read_per_join": "1M"
          },
          "used_columns": [
            "feature_id",
            "description",
            "full_description",
            "prefix",
            "suffix",
            "lang_code"
          ]
        }
      }
    ]
  }
}