SELECT 
  feature_id 
FROM 
  cscart_product_features 
WHERE 
  feature_id IN (
    23, 21, 29, 28, 26, 25, 27, 36, 35, 32, 31, 
    42, 45, 44, 43
  ) 
  AND feature_type = 'E'

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "10.93"
    },
    "table": {
      "table_name": "cscart_product_features",
      "access_type": "ALL",
      "possible_keys": [
        "PRIMARY"
      ],
      "rows_examined_per_scan": 41,
      "rows_produced_per_join": 1,
      "filtered": "3.66",
      "cost_info": {
        "read_cost": "10.63",
        "eval_cost": "0.30",
        "prefix_cost": "10.93",
        "data_read_per_join": "660"
      },
      "used_columns": [
        "feature_id",
        "feature_type"
      ],
      "attached_condition": "((`atulecarter_atul_demo2`.`cscart_product_features`.`feature_id` in (23,21,29,28,26,25,27,36,35,32,31,42,45,44,43)) and (`atulecarter_atul_demo2`.`cscart_product_features`.`feature_type` = 'E'))"
    }
  }
}