The data centers used for Masto.host are from OVH.
The shared hosting cloud is located in France.
Dedicated hosting allows for colocation of the dedicated service in other locations. France, Canada, London, Singapore, Poland, Germany and Australia. Depending on availability.
All servers run Debian.
The TLS (https) included are provided by Let's Encrypt.
Other software used: Node.js + Redis + PostgresSQL + Ruby + Nginx + Docker + OpenStack Swift.
Shared Hosting Infrastructure
Each Private VLAN can only communicate with the closest VLAN (in the graph) and under a specific number of ports.
Explanation and example of the flow: the public web can only access the host server. The host server can only communicate with the App Servers and only the App Servers can communicate with the databases.
With this setup the database is the hardest point to reach and none of the App Servers or Database Servers are accessible to the Public Web.
The media storage (Object Storage) is hosted directly with OVH and is completely independent from the Masto.host cloud.
The dedicated hosting setup will depend on the instance that it runs.
It can reach a complex setup like the one above or be a standard Mastodon install.