SELECT 
  * 
FROM 
  cscart_products 
WHERE 
  1 
  AND `enable_offer` = "E"

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_products",
          "access_type": "ALL",
          "rows": 310,
          "filtered": 100,
          "attached_condition": "cscart_products.enable_offer = 'E'"
        }
      }
    ]
  }
}