SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '420dd00095690f0c9266dd12cebbb6173aa951ee6d4f318946c9b811a7b594b2' 
  AND token = 'zxwyiMRcdRdRRL4ErH+V1pQi6v2+F6LhDTTunWrsob0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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