SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6bc294f82bceb6aa3c0413d2f380b31e6f4ae02296dfb1a8cf59784fc9188049' 
  AND token = 'FC4+uK7mfR3+LZ+lHvPWW5ftPlgv/xwcIAM5brMrCzs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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