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Four more answers from the developer in the FAQ: Tusky, what happens when users grow, why a local server, and why Cloudflare.
The Tusky answer states, with links to Tusky's own announcement and guide, what it was, when it shut down and the reason it gave. The scaling answer carries a measurement taken on the server's machine: 864 upload registrations per second with no failures. The two after it describe the machine, its backups and what Cloudflare does and sees. Answers link to each other where one leads to the next.