Gitlab dependency proxy is very slow

We have configured a project to used as a dependency proxy for maven packages. It technically works. The maven artifacts are downloaded to the package registry of this project, and those are again downloaded from the maven build that is being executed in a CI pipeline. The issue is that the downloading is very slow. We are seeing speeds in the 0-50 kb/s area. A build that would not go for longer than 5 minutes without proxy (complete re-download of all maven artifacts), can take an hour using the proxy.

I also notice that the maven packages that are downloaded for the project that is configured as dependency proxy, they all get their manually published date updated to the time of access. Not sure of the significance of this.

We are also using cache for the .m2 folder, so that the slowness of the dependency proxy is not detrimental, but this only works until we update the artifact dependencies to the latest versions.

Anyone know how to improve this?

Please add more details on your environment, based on the topic template:

🤗 _Please help fill in this template with all the details to help others help you more efficiently. Use [formatting blocks for code, config, logs](/t/community-first-steps-code-config-log-block-formatting-in-topics-and-replies/72138) and ensure to remove sensitive data._

###  Problem to solve 

*Describe your question in as much detail as possible:*

* *What are you seeing, and how does that differ from what you expect to see?*
* *Consider including screenshots, error messages, and/or other helpful visuals*

### Steps to reproduce 

*Which troubleshooting steps have you already taken? Can you link to any docs or other resources so we know where you have been?*

### Configuration

*Add the CI/CD configuration from `.gitlab-ci.yml` and other configuration if relevant (e.g. docker-compose.yml). Alternatively, create a public `GitLab.com` example project that provides all necessary files to reproduce the question.*

### Versions 

*Please select whether options apply, and add the version information.*

- [ ] Self-managed
- [ ] `GitLab.com` SaaS  
- [ ] Dedicated
- [ ] Self-hosted Runners

Versions 
- GitLab (Web: `/help` or self-managed system information `sudo gitlab-rake gitlab:env:info`):
- GitLab Runner, if self-hosted (Web `/admin/runners` or CLI  `gitlab-runner --version`):

### Helpful resources 

1. Check the [FAQ](/faq#product-resources) for helpful documentation, issues/bugs/feature proposals, and troubleshooting tips.
1. Before opening a new topic, make sure to search for keywords in the [forum search](/search)
1. Check the GitLab and GitLab Runner projects for existing issues. If you encounter a bug, please create a bug report issue.  
1. Review existing troubleshooting docs.

*Thanks for taking the time to be thorough in your request, it really helps!* 😊