The Shopping API platform exposes feeds over HTTPS with a streaming output.
Although not necessary, the streaming output allows you to start consuming offers without waiting for the file to finish downloading.
Feeds provided over HTTPS are compressed with gzip to optimize bandwith and limit the time you need to download them.
All modern tools and libraries are able to handle both streaming and gzip natively. Most of the time, you just need to use the correct configuration or method of your library.
Technical details
From a technical perspective, what we are calling streaming is actually a HTTP response with the headers Transfer-Encoding: chunked and Content-Encoding: gzip.
You can find more details on Mozilla Developer Network.
From a linux shell (cURL)
For testing purposes or if you are consuming feeds from a shell script, you can call the Shopping Feeds streaming API with following cURL command:
curl --compressed "http://api.kelkoogroup.net/publisher/..."
This will output all the content of the feed in small chunks.
From a Java based application
If you are consuming the feeds from a Java-based application, you can use your favorite HTTP library (Apache HTTP Client for instance) or the latest HttpClient provided from Java11 onwards.
Please ensure that your client is providing the Accept-Encoding: gzip header (it is set by default in the usual clients).