You can see all the job openings at https://boards.greenhouse.io/grafanalabs and read more about Grafana Labs here: https://grafana.com/about/careers/#jobs
I work on the Alerting team and we are looking for a backend engineer (remote EST, https://boards.greenhouse.io/grafanalabs/jobs/4857517004) to work on Grafana Alerting which is based on the Prometheus Alertmanager. The code you would be working on is mostly part of https://github.com/grafana/grafana and, if you want to learn more about the context we are in, I recommend you to watch this presentation from our tech lead: https://youtu.be/9AX8u-bt4J8