Comment by nikeee
I've built an S3 client with similar goals like TFA, but supports pre-signing:
https://github.com/nikeee/lean-s3
Pre-signing is about 30 times faster than the AWS SDK and is not async.
You can read about why it looks like it does here: https://github.com/nikeee/lean-s3/blob/main/DESIGN_DECISIONS...
FYI, you can add browser support by using noble-hashes[1] for SHA256/HMAC - it's a well-done library, and gives you performance that is indistinguishable from native crypto on any scale relevant to S3 operations. We use it for our in-house S3 client.
[1] https://github.com/paulmillr/noble-hashes