SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8763fd5a3523a4d82a97482efb9cba59a8d5bd3a505b629785d00f9d24364220' 
  AND token = 'CWxfF+BCjqUEzCQDKY0pBl9rhml11rxJz2MpCDRcBDc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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