SELECT 
  * 
FROM 
  cscart_sg_gift_certificate 
WHERE 
  1 
  AND status = 'A' 
  and use_for_merchant_gift = 'N' 
  and use_for_member_gift = 'N'

Query time 0.00048

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.0113438,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_sg_gift_certificate",
          "access_type": "ALL",
          "loops": 1,
          "rows": 3,
          "cost": 0.0113438,
          "filtered": 100,
          "attached_condition": "cscart_sg_gift_certificate.`status` = 'A' and cscart_sg_gift_certificate.use_for_merchant_gift = 'N' and cscart_sg_gift_certificate.use_for_member_gift = 'N'"
        }
      }
    ]
  }
}