Plack::Middleware::Deflater is a middleware to encode your response body
in gzip or deflate, based on "Accept-Encoding" HTTP request header. It
would save the bandwidth a little bit but should increase the Plack server
load, so ideally you should handle this on the frontend reverse proxy
servers.

This middleware removes "Content-Length" and streams encoded content,
which means the server should support HTTP/1.1 chunked response or
downgrade to HTTP/1.0 and closes the connection.