SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '834661ce83d4063a7be95726574b352071683225e8fb962058fae7f9898af56d' 
  AND token = 'ZQSiMxGfTvNPLcUSQn8fA0EFgptaUFHCQ5UKlPnPDEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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