bring back portable services

Signed-off-by: Xe Iaso <me@xeiaso.net>

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+# XeDN
+
+Xe's CDN replacement service
+
+## Goal
+
+XeDN is a CDN replacement service. It is a tool that enables you to
+serve files from a central storage pool (such as Backblaze B2) in a
+way that caches all those files locally. This lets you put several
+instances of XeDN in different datacentres globally and then each
+instance will act as a local cache. This strategy lets you decrease
+observable latency for users.
+
+The goal of this service is to replace Cloudflare for my own uses.
+
+## Design
+
+At a high level, XeDN is a caching HTTP proxy. It caches files locally
+using [BoltDB](https://github.com/etcd-io/bbolt) and serves from that
+cache whenever possible. XeDN pulls files from its source (currently
+over HTTP, but this can be changed in the future) and aggressively
+caches them in the database. When each file is cached, it has a
+default lifetime of one week. This lifetime is extended every time a
+file is requested, hopefully making sure that each file that is
+commonly used is never requested from backend servers. This does make
+genuinely updating content hard, so users of XeDN are encouraged to
+assume that the backend is an _append-only_ store.
+