How can I speed up the syncing process of Synology Drive?

Purpose

Many factors can slow down the syncing speed of Synology Drive, such as the QuickConnect server bottleneck or transfer speed limitations.

If you connect to Synology Drive through QuickConnect, switch to a direct connection method, such as DDNS. Refer to this article on how to set up port forwarding¹ and DDNS for Synology Drive.
Make sure the transfer speed is not restricted by Traffic Control settings. Refer to this article for more information.
Make sure you have given sufficient speed limit quota to Synology Drive Server in Control Panel > User & Group. Refer to this article for more information.

Notes:

For file syncing, use port 6690. For link sharing, use ports 5000/5001 or 80/443.