I found the cause: it's the signature verification method.
Removing it the size (unzipped) is 642kb.
The verify signature method internally call only `secp.verify_schnorr` method (`secp256k1` library).
Discussion
Indeed.
The size become much sumaller after removing the verify code.
Total Upload: 575.34 KiB / gzip: 299.15 KiB
I hope we can find an alternative as I don't want to save invalid data.