SELECT 
  COUNT(*) 
FROM 
  cscart_product_features 
WHERE 
  display_on_key_product_info = 'Y'

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "11.60"
    },
    "table": {
      "table_name": "cscart_product_features",
      "access_type": "ALL",
      "rows_examined_per_scan": 106,
      "rows_produced_per_join": 10,
      "filtered": "10.00",
      "cost_info": {
        "read_cost": "10.54",
        "eval_cost": "1.06",
        "prefix_cost": "11.60",
        "data_read_per_join": "4K"
      },
      "used_columns": [
        "display_on_key_product_info"
      ],
      "attached_condition": "(`cscart_db`.`cscart_product_features`.`display_on_key_product_info` = 'Y')"
    }
  }
}