Slow artifact creation and upload

My GitLab setup consists of multiple runners that are on different locations (East coast, West coast). The Gitlab server is located on the West coast. Each time a build is happening on the remote runner on the East coast, the artifact creation and upload takes a long time. The artifact zip is about 100 MB and the bandwidth is not really the issue. This file file could be uploaded in less than a minute, but here it takes an extra 15 min instead. The artifacts contains around 2,000 files.

I am wondering if the latency is causing this, combined with multiple upload requests to the server (per file?). Or is there any tweak I could perform?