Improving your local network's bandwidth or optimizing the concurrent connection handling on your system might ease the upload process temporarily. Until the new optimizations are fully deployed, adjusting local system resources and configurations could be beneficial. Consider checking for any updates or optimizations announced for the Walrus node as they're working on caching improvements that could directly impact upload times.

The slowness you're experiencing during uploads is indeed partially due to the erasure coding process handled on the client side. The developers are optimizing this to improve the user experience when handling multiple blobs. Currently, Walrus nodes can handle up to 8 concurrent HTTP requests for blob storage due to the default configuration of 8 sub-wallets. Increasing this limit may improve upload speed but will depend on your network capacity and node configuration. You can increase the default PUT request limit, which is set at 10 MiB, through the '--max-body-size' option. This can help manage larger uploads more effectively.