Walrus has a maximum blob size limit of 13.6 GiB, so your 300MB file should not exceed the system's capabilities. However, default PUT requests are limited to 10 MiB; you can increase this limit by configuring your own publisher or adjusting the --max-body-size option.

Using a local setup with the appropriate configurations might help bypass some network limitations, potentially improving speeds. For future uploads, you can use the walrus info command to check current configurations for any predefined limits or conditions that might affect file uploads.

The slow upload speed you're experiencing on the CLI could be influenced by several factors such as network issues, server throttling, or limitations set by the server to manage high loads.