SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    11047, 11048, 11049, 11050, 11051, 11052, 
    11053, 11054, 11055, 11056, 11057, 
    11058, 11059, 11060, 11061, 11062, 
    11063, 11065, 11066, 11064
  ) 
  AND feature_id IN (553, 624, 623) 
  AND lang_code = 'en'

Query time 0.00432

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "14.92"
    },
    "table": {
      "table_name": "cscart_product_features_values",
      "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",
        "feature_id",
        "lang_code"
      ],
      "key_length": "12",
      "rows_examined_per_scan": 64,
      "rows_produced_per_join": 64,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "8.52",
        "eval_cost": "6.40",
        "prefix_cost": "14.92",
        "data_read_per_join": "49K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (11047,11048,11049,11050,11051,11052,11053,11054,11055,11056,11057,11058,11059,11060,11061,11062,11063,11065,11066,11064)) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (553,624,623)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}

Result

product_id feature_id variant_id
11047 553 1324
11047 623 1983
11047 624 1705
11048 553 1324
11048 623 2095
11048 624 1705
11049 553 1324
11049 623 2096
11049 624 1705
11050 553 1324
11050 623 2097
11050 624 1705
11051 553 1324
11051 623 2085
11051 624 1705
11052 553 1324
11052 623 2086
11052 624 1705
11053 553 1324
11053 623 2087
11053 624 1705
11054 553 1324
11054 623 2088
11054 624 1705
11055 553 1324
11055 623 2089
11055 624 1705
11056 553 1324
11056 623 2090
11056 624 1705
11057 553 2197
11057 623 1983
11057 624 1705
11058 553 2197
11058 623 2095
11058 624 1705
11059 553 2197
11059 623 2096
11059 624 1705
11060 553 2197
11060 623 2097
11060 624 1705
11061 553 2197
11061 623 2085
11061 624 1705
11062 553 2197
11062 623 2086
11062 624 1705
11063 553 2197
11063 623 2087
11063 624 1705
11064 553 2197
11064 623 2088
11064 624 1705
11065 553 2197
11065 623 2089
11065 624 1705
11066 553 2197
11066 623 2090
11066 624 1705