SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b51689eca81eee959fefaee259f01ed204db333c7222f500c9fc40662a61b664' 
  AND token = 'n/fTUEnfTVFUeYNyBXzVwJgom8i5uZZGse/ZFgzaJsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}