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, 
  cscart_product_feature_variants.mdc_variant 
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 = 346 
  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' 
WHERE 
  1 
  AND cscart_product_feature_variants.feature_id IN (
    1055, 1080, 1041, 1057, 1046, 1050, 1072, 
    1059, 1047, 1073, 1074, 1071, 1067, 
    1061, 1064, 1065, 1044, 1069, 1076, 
    1078, 1079, 1135, 1056, 1052, 1063, 
    1070, 1042, 1077, 1066, 1054, 1084, 
    1136, 1062, 1043, 1053, 1075, 1083, 
    1060, 1068, 1085, 1081, 1082, 1086, 
    1045
  ) 
GROUP BY 
  cscart_product_feature_variants.variant_id 
ORDER BY 
  cscart_product_feature_variants.position, 
  cscart_product_feature_variant_descriptions.variant

Query time 0.00404

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "49.72"
    },
    "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": "ref",
              "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"
              ],
              "key_length": "3",
              "ref": [
                "const"
              ],
              "rows_examined_per_scan": 11,
              "rows_produced_per_join": 5,
              "filtered": "51.27",
              "using_index": true,
              "cost_info": {
                "read_cost": "1.40",
                "eval_cost": "1.13",
                "prefix_cost": "3.60",
                "data_read_per_join": "4K"
              },
              "used_columns": [
                "feature_id",
                "product_id",
                "variant_id",
                "lang_code"
              ],
              "attached_condition": "((`danishecarter_25_march`.`cscart_product_features_values`.`feature_id` in (1055,1080,1041,1057,1046,1050,1072,1059,1047,1073,1074,1071,1067,1061,1064,1065,1044,1069,1076,1078,1079,1135,1056,1052,1063,1070,1042,1077,1066,1054,1084,1136,1062,1043,1053,1075,1083,1060,1068,1085,1081,1082,1086,1045)) and (`danishecarter_25_march`.`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": [
                "danishecarter_25_march.cscart_product_features_values.variant_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 4,
              "filtered": "87.85",
              "cost_info": {
                "read_cost": "5.64",
                "eval_cost": "0.99",
                "prefix_cost": "10.37",
                "data_read_per_join": "13K"
              },
              "used_columns": [
                "variant_id",
                "feature_id",
                "position",
                "mdc_variant"
              ],
              "attached_condition": "(`danishecarter_25_march`.`cscart_product_feature_variants`.`feature_id` = `danishecarter_25_march`.`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": [
                "danishecarter_25_march.cscart_product_features_values.feature_id"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 4,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "4.95",
                "eval_cost": "0.99",
                "prefix_cost": "16.32",
                "data_read_per_join": "5K"
              },
              "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": [
                "danishecarter_25_march.cscart_product_features_values.variant_id",
                "const"
              ],
              "rows_examined_per_scan": 1,
              "rows_produced_per_join": 4,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "4.95",
                "eval_cost": "0.99",
                "prefix_cost": "22.26",
                "data_read_per_join": "14K"
              },
              "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": [
                "danishecarter_25_march.cscart_product_features_values.variant_id",
                "const",
                "const",
                "const"
              ],
              "rows_examined_per_scan": 4,
              "rows_produced_per_join": 19,
              "filtered": "100.00",
              "cost_info": {
                "read_cost": "23.49",
                "eval_cost": "3.96",
                "prefix_cost": "49.72",
                "data_read_per_join": "33K"
              },
              "used_columns": [
                "name",
                "object_id",
                "type",
                "dispatch",
                "path",
                "lang_code"
              ]
            }
          }
        ]
      }
    }
  }
}

Result

variant variant_id feature_id selected feature_type seo_name seo_path mdc_variant
1000 23093 1042 23093 S 1000
10518 26015 1073 26015 N 10518
11 25421 1059 25421 N 11
12 L/100 km 25441 1065 25441 S 12
14 Days 24088 1055 24088 S 14_days
150 25429 1060 25429 N 150
15000 Kg 25545 1083 25545 S 15000
15478526 26045 1063 26045 N
18 months 25502 1076 25502 S 18
2 26046 1077 26046 N
2/3 25495 1074 25495 S TWO_OR_THREE
2000 25530 1081 25530 S 2000
2002 26042 1046 26042 N
200904 26010 1064 26010 N 200904
2500 25540 1082 25540 S 2500
294 26012 1062 26012 N 294
3500 26030 1052 26030 N 3500
4 25445 1066 25445 N 4
4 (Green) 25430 1061 25430 S EMISSIONSSTICKER_GREEN
65 26047 1135 26047 N
Adaptive Cruise Control 25485 1072 25485 S ADAPTIVE_CRUISE_CONTROL
Ads with pictures 24079 1054 24079 M ads_with_pictures
Automatic air conditioning 25400 1057 25400 S AUTOMATIC_CLIMATISATION
Black 25507 1078 25507 S BLACK
BMW 24409 1056 24409 E bmw BMW
Brown 25471 1070 25471 S BROWN
Camera 25549 1084 25549 M REAR_VIEW_CAM
Caravan 24179 1041 24179 S Caravan
Dealer 24073 1053 24073 S dealer
Ethanol (FFV, E85, etc.) 23799 1044 23799 S ETHANOL
Euro2 25451 1067 25451 S EURO2
Front 25547 1084 25547 M FRONT_SENSORS
Front and Side Airbags 25523 1080 25523 S FRONT_AND_SIDE_AIRBAGS
Front wheel drive 25481 1071 25481 S FRONT
Full leather 25514 1079 25514 S LEATHER
Germany 23864 1050 23864 S DE
Jaguar APPROVED 25564 1086 25564 S JAGUAR
Leasing 26041 1136 26041 S l
Leasing only 23791 1043 23791 S LEASING_ONLY
Removable or swiveling 25553 1085 25553 S frs
Semi-automatic 25466 1069 25466 S SEMIAUTOMATIC_GEAR
Sliding door left 25499 1075 25499 S SLIDING_DOOR_LEFT
Trailer coupling, swiveling 25463 1068 25463 S TRAILER_COUPLING_SWIVELING
Used vehicle 23802 1045 23802 S USED
Yes 23804 1047 23804 S Y