I think that the lightest you can get is SNAC: written in portable C, it requires only an ngix server, and no database.

It’s ideal for single used instances or automated projects

Here some background and how tos: …tesio.it/…/how-to-run-your-own-social-network.ht…

And here the description of fedimeteo, that provides forecasts for thousands of cities on the fediverse using a slim low cost vps’ …dragas.net/…/fedimeteo-how-a-tiny-freebsd-vps-be…