SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    11005, 11006, 11007, 11008, 11009, 11010, 
    11011, 11012, 11013, 11014, 11015, 
    11016, 11017, 11018, 11019, 11020, 
    11021, 11022, 11023, 11024, 11025, 
    11026
  ) 
  AND feature_id IN (553, 624, 623) 
  AND lang_code = 'en'

Query time 0.00616

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "15.36"
    },
    "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": 66,
      "rows_produced_per_join": 66,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "8.76",
        "eval_cost": "6.60",
        "prefix_cost": "15.36",
        "data_read_per_join": "51K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (11005,11006,11007,11008,11009,11010,11011,11012,11013,11014,11015,11016,11017,11018,11019,11020,11021,11022,11023,11024,11025,11026)) 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
11005 553 1324
11005 623 1975
11005 624 1705
11006 553 1324
11006 623 2082
11006 624 1705
11007 553 1324
11007 623 2092
11007 624 1705
11008 553 1324
11008 623 2083
11008 624 1705
11009 553 1324
11009 623 2084
11009 624 1705
11010 553 1324
11010 623 2085
11010 624 1705
11011 553 1324
11011 623 2086
11011 624 1705
11012 553 1324
11012 623 2087
11012 624 1705
11013 553 1324
11013 623 2088
11013 624 1705
11014 553 1324
11014 623 2089
11014 624 1705
11015 553 1324
11015 623 2093
11015 624 1705
11016 553 2197
11016 623 1975
11016 624 1705
11017 553 2197
11017 623 2082
11017 624 1705
11018 553 2197
11018 623 2092
11018 624 1705
11019 553 2197
11019 623 2083
11019 624 1705
11020 553 2197
11020 623 2084
11020 624 1705
11021 553 2197
11021 623 2085
11021 624 1705
11022 553 2197
11022 623 2086
11022 624 1705
11023 553 2197
11023 623 2087
11023 624 1705
11024 553 2197
11024 623 2088
11024 624 1705
11025 553 2197
11025 623 2089
11025 624 1705
11026 553 2197
11026 623 2093
11026 624 1705