SELECT 
  product_id, 
  feature_id, 
  variant_id 
FROM 
  cscart_product_features_values 
WHERE 
  product_id IN (
    11298, 11297, 11296, 11295, 11294, 11293, 
    11292, 11291, 11290, 11289, 11288, 
    11287, 11286, 11285, 11284, 11283, 
    11282, 11281, 11280, 11279
  ) 
  AND feature_id IN (553, 624, 623) 
  AND lang_code = 'en'

Query time 0.00282

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "16.26"
    },
    "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": 70,
      "rows_produced_per_join": 70,
      "filtered": "100.00",
      "using_index": true,
      "cost_info": {
        "read_cost": "9.26",
        "eval_cost": "7.00",
        "prefix_cost": "16.26",
        "data_read_per_join": "54K"
      },
      "used_columns": [
        "feature_id",
        "product_id",
        "variant_id",
        "lang_code"
      ],
      "attached_condition": "((`gaseus`.`cscart_product_features_values`.`product_id` in (11298,11297,11296,11295,11294,11293,11292,11291,11290,11289,11288,11287,11286,11285,11284,11283,11282,11281,11280,11279)) and (`gaseus`.`cscart_product_features_values`.`feature_id` in (553,624,623)) and (`gaseus`.`cscart_product_features_values`.`lang_code` = 'en'))"
    }
  }
}