I have looked at eulalie and am currently puttering around with cljs-lambda - I think the easiest thing to do would be to fork it, cp src/eulalie/dynamo.cljc src/eulalie/s3.cljc and re-customize the file

which would primarily consist, I think, of s/dynamo/s3/g, looking up the right service prefix, and then in your client code building the right kind of request objects (`GetObject`, PutObject, etc.) - multipart uploads will certainly be the heaviest lifting from a complexity perspective