We use a mix of different providers, combined it's approximately ~20Gbit outbound with unlimited traffic.
Our main servers are 2x 40tb raw servers, we set them up with RAID0 which leaves us with ~36tb usable. These store the most recent version of every game we index.
We also utilize two cache servers in the EU and two in NA, these have ~200gb disk so they constantly rotate out old torrents for newly added torrents. Their main purpose is to absorb the initial flood of traffic and help speed up the swarm.
For backend services, we mostly use a mix of differently sized VPS's, connected via their own VLAN.
We currently use three reverse proxies running Openresty. SSL is terminated at these proxies and we then re-encrypt the traffic between our proxies and our backend. Internally, everything runs on non-default ports with specific firewall rules.
Lets Encrypt is used for our SSL.
Jenkins and Ansible is how we handle automation.
We use Torrust for the backend - Github.
We use Ghost for rpdl.net and Umami for our analytics.
For torrents, we use Qbittorrent-nox and Flood to give us API access.