SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '28f91263ace5be3debe6330d4b95987c019901cad0f39ee3ac8082d86180756b' 
  AND token = 'BAg3RmW5rWv9ysqFS0HwHKFHKH0MpiyCUzS/Pon951M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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