I would probably use JSONEncode on my table to convert it into JSON, and then use an open-source gzip script to compress it. And then encode the result into Base64.
EDIT: This seems promising: https://github.com/Rochet2/lualzw. I’m not sure that the algorithm is gzip, however EDITEDIT: It’s not gzip, sadly.
Huh. looking for a gzip library was harder than I thought.
Also keep in mind, if you do compress your data in Lua, I don’t think you’ll be able to use PostAsync due to the fact that you cannot set the gzip header (to indicate to the server that your data is compressed)