SELECT 
  feature_id, 
  feature_type 
FROM 
  cscart_product_features 
WHERE 
  feature_id IN (560, 18, 562, 561, 548)

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.00702747,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_features",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["feature_id"],
          "loops": 1,
          "rows": 5,
          "cost": 0.00702747,
          "filtered": 100,
          "attached_condition": "cscart_product_features.feature_id in (560,18,562,561,548)"
        }
      }
    ]
  }
}