auth-gateway

auth-gateway is an authentication gateway for Cortex, the multi-tenant, long-term storage for Prometheus.

Cortex supports multi-tenancy, but it leaves tenant authentication to you. Most teams ended up hand-rolling an NGINX reverse proxy for it, which is fiddly to set up and limited. auth-gateway replaces that with a small Go service. You declare your tenants in a simple config, and it authenticates each request and routes it to the right Cortex backend.

The Internship

I built it during a three-month internship through the Linux Foundation’s LFX Mentorship program. My mentor was Friedrich Gonzalez, a Cortex maintainer and Cloud Operations Software Engineer at Adobe. He broke the project into small, well-scoped tasks so I could ship from the first week, and his reviews shaped how I write and structure code to this day.

It was also my first time building in the open. I wrote a design proposal for the Cortex maintainers, worked through their review, and joined the community’s calls and discussions. I learned how open-source decisions actually get made: in public threads, through consensus, with people across time zones. I also learned to get feedback from users before building features nobody asked for. I picked up Go along the way and stayed on as the project’s maintainer after the program ended.

I wrote about the full experience in A Transformative Journey: My Experience as an LFX Mentee.