I think I might combine the two, with

(post ... #:json x)

being a shorthand for

(post ... #:data (json-payload x))

This might make supporting compression and file uploads easier + it seems like it’ll simplify the implementation.

Compression worked out to just

(post #:data (gzip-payload (json-payload x)) ...) which I think is pretty good.

wow, a payload combinator!