SELECT 
  cscart_product_feature_variant_descriptions.variant, 
  cscart_product_feature_variants.variant_id, 
  cscart_product_feature_variants.feature_id, 
  cscart_product_features_values.variant_id as selected, 
  cscart_product_features.feature_type, 
  cscart_seo_names.name as seo_name, 
  cscart_seo_names.path as seo_path 
FROM 
  cscart_product_feature_variants 
  LEFT JOIN cscart_product_feature_variant_descriptions ON cscart_product_feature_variant_descriptions.variant_id = cscart_product_feature_variants.variant_id 
  AND cscart_product_feature_variant_descriptions.lang_code = 'en' 
  INNER JOIN cscart_product_features_values ON cscart_product_features_values.variant_id = cscart_product_feature_variants.variant_id 
  AND cscart_product_features_values.lang_code = 'en' 
  AND cscart_product_features_values.product_id = 3473 
  AND cscart_product_features_values.feature_id = cscart_product_feature_variants.feature_id 
  LEFT JOIN cscart_product_features ON cscart_product_features.feature_id = cscart_product_feature_variants.feature_id 
  LEFT JOIN cscart_seo_names ON cscart_seo_names.object_id = cscart_product_feature_variants.variant_id 
  AND cscart_seo_names.type = 'e' 
  AND cscart_seo_names.dispatch = '' 
  AND cscart_seo_names.lang_code = 'en' 
  AND (
    cscart_seo_names.company_id = 1 
    OR cscart_seo_names.company_id = 0
  ) 
WHERE 
  1 
  AND cscart_product_feature_variants.feature_id IN (
    621, 594, 595, 550, 628, 624, 625, 626, 
    622, 623, 605, 606, 627, 634, 636, 629, 
    637, 631
  ) 
GROUP BY 
  cscart_product_feature_variants.variant_id 
ORDER BY 
  cscart_product_feature_variants.position, 
  cscart_product_feature_variant_descriptions.variant

Query time 0.00422

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "36.53"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": false,
        "nested_loop": [
          {
            "table": {
              "table_name": "cscart_product_features_values",
              "access_type": "range",
              "possible_keys": [
                "PRIMARY",
                "fl",
                "variant_id",
                "lang_code",
                "product_id",
                "fpl",
                "idx_product_feature_variant_id"
              ],
              "key": "idx_product_feature_variant_id",
              "used_key_parts": [
                "product_id",
                "feature_id",
                "lang_code"
              ],
              "key_length": "12",
              "rows_examined_per_scan": 25,
              "rows_produced_per_join": 25,
              "filtered": "100.00",
              "using_index": true,
              "cost_info": {
                "read_cost": "3.68",
                "eval_cost": "2.50",
                "prefix_cost": "6.18",
                "data_read_per_join": "19K"
              },
              "used_columns": [
                "feature_id",
                "product_id",
                "variant_id",
                "lang_code"
              ],
              "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` = 3473) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (621,594,595,550,628,624,625,626,622,623,605,606,627,634,636,629,637,631)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
            }
          },
          {
            "table": {
              "table_name": "cscart_product_feature_variants",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY",
                "feature_id"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "variant_id"
              ],
              "key_length": "3",
              "ref": [
                "gaseus.cscart_product_features_values.variant_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 20,
              "filtered": "82.28",
              "cost_info": {
                "read_cost": "6.25",
                "eval_cost": "2.06",
                "prefix_cost": "14.93",
                "data_read_per_join": "23K"
              },
              "used_columns": [
                "variant_id",
                "feature_id",
                "position"
              ],
              "attached_condition": "(`gaseus`.`cscart_product_feature_variants`.`feature_id` = `gaseus`.`cscart_product_features_values`.`feature_id`)"
            }
          },
          {
            "table": {
              "table_name": "cscart_product_features",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "feature_id"
              ],
              "key_length": "3",
              "ref": [
                "gaseus.cscart_product_features_values.feature_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 20,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "5.14",
                "eval_cost": "2.06",
                "prefix_cost": "22.13",
                "data_read_per_join": "24K"
              },
              "used_columns": [
                "feature_id",
                "feature_type"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_product_feature_variant_descriptions",
              "access_type": "eq_ref",
              "possible_keys": [
                "PRIMARY"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "variant_id",
                "lang_code"
              ],
              "key_length": "9",
              "ref": [
                "gaseus.cscart_product_features_values.variant_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 20,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "5.14",
                "eval_cost": "2.06",
                "prefix_cost": "29.33",
                "data_read_per_join": "64K"
              },
              "used_columns": [
                "variant_id",
                "variant",
                "lang_code"
              ]
            }
          },
          {
            "table": {
              "table_name": "cscart_seo_names",
              "access_type": "ref",
              "possible_keys": [
                "PRIMARY",
                "dispatch"
              ],
              "key": "PRIMARY",
              "used_key_parts": [
                "object_id",
                "type",
                "dispatch",
                "lang_code"
              ],
              "key_length": "206",
              "ref": [
                "gaseus.cscart_product_features_values.variant_id",
                "const",
                "const",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 20,
              "filtered": "100.00",
              "index_condition": "<if>(is_not_null_compl(cscart_seo_names), ((`gaseus`.`cscart_seo_names`.`company_id` = 1) or (`gaseus`.`cscart_seo_names`.`company_id` = 0)), true)",
              "cost_info": {
                "read_cost": "5.14",
                "eval_cost": "2.06",
                "prefix_cost": "36.53",
                "data_read_per_join": "34K"
              },
              "used_columns": [
                "name",
                "object_id",
                "company_id",
                "type",
                "dispatch",
                "path",
                "lang_code"
              ]
            }
          }
        ]
      }
    }
  }
}

Result

variant variant_id feature_id selected feature_type seo_name seo_path
200 1707 631 1707 S
200 1705 624 1705 N
32490323 1775 621 1775 S
4 2139 625 2139 N
5 1718 626 1718 N
Automotive Industry 1663 605 1663 M
Cutting 1667 605 1667 M
Cylinder regulators 1933 550 1933 S
DIN EN ISO 2503 1447 594 1447 S
EPDM 1661 629 1661 S
G 1/4 RHk x 6mm 1720 623 1720 S
Manufacturing Industry 1669 605 1669 M
Medical Technology 1662 605 1662 M
Nitrogen (N2) 1905 595 1905 S
Petrochemical Industry 1664 605 1664 M
Pharmaceutical Industry 1665 605 1665 M
Research & Development 1668 605 1668 M
Single stage 1660 628 1660 S
Technical gases 1401 606 1401 M
W 24,32 x 1/14 RH 1703 622 1703 S
Welding 1666 605 1666 M
Y 2352 634 2352 S
Y 2348 636 2348 S
Y 2350 637 2350 S
Brass 1659 627 1659 S