SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5208eae054ba4b0e6fa2499422b1fe33371eea3e2d8c0520991b400c41139b95' 
  AND token = 'Rk51+4zFnyEz5t26z9Mx0LzQuIFI/Q9dw+FWNZaebT0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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