SELECT 
  feature_id, 
  filter_style 
FROM 
  cscart_product_features 
WHERE 
  feature_id IN (549, 596)

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0042687,
    "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": 2,
          "cost": 0.0042687,
          "filtered": 100,
          "attached_condition": "cscart_product_features.feature_id in (549,596)"
        }
      }
    ]
  }
}