SELECT 
  `P`.`product_id`, 
  `PFD`.`internal_name` AS `name`, 
  `PFVD`.`variant`, 
  `PFVD`.`variant_id`, 
  `PFD`.`feature_id` 
FROM 
  `cscart_product_features_values` AS `PFV` 
  JOIN `cscart_product_features` AS `PF` ON `PFV`.`feature_id` = `PF`.`feature_id` 
  JOIN `cscart_products` AS `P` ON `P`.`product_id` = `PFV`.`product_id` 
  JOIN `cscart_product_features_descriptions` AS `PFD` ON `PFV`.`feature_id` = `PFD`.`feature_id` 
  JOIN `cscart_product_feature_variants` AS `PFVS` ON `PFVS`.`variant_id` = `PFV`.`variant_id` 
  JOIN `cscart_product_feature_variant_descriptions` AS `PFVD` ON `PFVS`.`variant_id` = `PFVD`.`variant_id` 
WHERE 
  1 
  AND `PF`.`status` = 'A' 
  AND `PFV`.`product_id` IN(
    '5391', '5387', '5388', '5389', '5386'
  )

Query time 0.00108

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "42.82"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "P",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY",
            "cscart_products_product_id_index"
          ],
          "key": "cscart_products_product_id_index",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 5,
          "rows_produced_per_join": 5,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "0.76",
            "eval_cost": "0.50",
            "prefix_cost": "1.26",
            "data_read_per_join": "37K"
          },
          "used_columns": [
            "product_id"
          ],
          "attached_condition": "(`dev2`.`P`.`product_id` in ('5391','5387','5388','5389','5386'))"
        }
      },
      {
        "table": {
          "table_name": "PFV",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY",
            "fl",
            "variant_id",
            "product_id",
            "fpl",
            "idx_product_feature_variant_id"
          ],
          "key": "product_id",
          "used_key_parts": [
            "product_id"
          ],
          "key_length": "3",
          "ref": [
            "dev2.P.product_id"
          ],
          "rows_examined_per_scan": 6,
          "rows_produced_per_join": 30,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "1.79",
            "eval_cost": "3.06",
            "prefix_cost": "6.11",
            "data_read_per_join": "23K"
          },
          "used_columns": [
            "feature_id",
            "product_id",
            "variant_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "PF",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY",
            "status"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id"
          ],
          "key_length": "3",
          "ref": [
            "dev2.PFV.feature_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 24,
          "filtered": "80.46",
          "cost_info": {
            "read_cost": "7.65",
            "eval_cost": "2.46",
            "prefix_cost": "16.82",
            "data_read_per_join": "38K"
          },
          "used_columns": [
            "feature_id",
            "status"
          ],
          "attached_condition": "(`dev2`.`PF`.`status` = 'A')"
        }
      },
      {
        "table": {
          "table_name": "PFVS",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "dev2.PFV.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 24,
          "filtered": "100.00",
          "using_index": true,
          "cost_info": {
            "read_cost": "6.16",
            "eval_cost": "2.46",
            "prefix_cost": "25.44",
            "data_read_per_join": "37K"
          },
          "used_columns": [
            "variant_id"
          ]
        }
      },
      {
        "table": {
          "table_name": "PFD",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "feature_id"
          ],
          "key_length": "3",
          "ref": [
            "dev2.PFV.feature_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 24,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "6.16",
            "eval_cost": "2.49",
            "prefix_cost": "34.09",
            "data_read_per_join": "68K"
          },
          "used_columns": [
            "feature_id",
            "internal_name"
          ]
        }
      },
      {
        "table": {
          "table_name": "PFVD",
          "access_type": "ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "ref": [
            "dev2.PFV.variant_id"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 24,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "6.23",
            "eval_cost": "2.50",
            "prefix_cost": "42.82",
            "data_read_per_join": "105K"
          },
          "used_columns": [
            "variant_id",
            "variant"
          ]
        }
      }
    ]
  }
}