SELECT 
  feature_id, 
  feature_type 
FROM 
  cscart_product_features 
WHERE 
  feature_id IN (903, 904, 825, 827, 826, 901)

Query time 0.00044

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "14.41"
    },
    "table": {
      "table_name": "cscart_product_features",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "feature_id"
      ],
      "key_length": "3",
      "rows_examined_per_scan": 6,
      "rows_produced_per_join": 6,
      "filtered": "100.00",
      "index_condition": "(`danishecarter_latest`.`cscart_product_features`.`feature_id` in (903,904,825,827,826,901))",
      "cost_info": {
        "read_cost": "13.21",
        "eval_cost": "1.20",
        "prefix_cost": "14.41",
        "data_read_per_join": "7K"
      },
      "used_columns": [
        "feature_id",
        "feature_type"
      ]
    }
  }
}