microcosm 2025

Microcosm is community infrastructure and self-hostable API services that make building on atproto fast and easy. In late February we kicked things off with the initial release of Constellation , a universal backlinks index that automatically works with all lexicons.

It's often easy for me to forget, but a lot else happened in 2025! This post has many lists of things I want to remember, but the best part of this year was meeting and being inspired by so many wonderful people in the community. The year wasn't easy in many ways, but you all have motivated me to get through it. Here's to even more in 2026.

If you're able, sponsoring me on github or supporting me on ko-fi helps this all keep going!

Community & Events

The microcosm discord server grew to 66 members. We won't stay with discord forever, but for now it's nice. Join, if you want !

Presented at atmosphereconf

Presented at atproTO toronto meetup

Attended IETF 124 in Montreal

Built with microcosm

I didn't do a great job of keeping track of all the projects people have launched using microcosm services! This is not a complete list! Let me know if I missed your project, I would love to add it!

PDS browsers pdsls.dev , atp.tools , and atexplore.social : constellation for backlinks

anisota.net : constellation for record viewer backlinks +more

at://giveaways : constellation for enumerating like and comment entries

at-toolbox : constellation actions

excuse : microcosm us-east jetstream

nucleus appview-less bluesky client: microcosm slingshot, constellation, spacedust, and jetstream.

wafrn : microcosm jetstream

cutebook : microcosm constellation, self-hosted(!) slingshot

wisp.place : microcosm slingshot

ewancroft.uk : slingshot, constellation

red dwarf : slingshot, constellation

witchsky.app : constellation

leaflet.pub : constellation for quotes and mentions

alpha.weaver.sh : constellation, slingshot, UFOs API

Blacksky : constellation and slingshot

atcute : built-in support for microcosm XRPC APIs

skythread : constellation

kibun embed : slingshot

deer.social : constellation for peer-to-peer verifications

...and every fork of deer.social

a lexicon analysis by Ms Boba : UFOs API

Bluesky Jetstream Live : microcosm jetstreams

traverse.connectedplaces.online : constellation, slingshot

Verified accounts tracker : constellation

Pattern : constellation for contextual neighbour comments

a feed recommendation system from @l4.pm : constellation for like-neighbours

dropanchor.app : slingshot

atproto-snake : slingshot

leaflet-loader-astro : slingshot

skylite : spacedust

tangled issue search : constellation and slingshot

teal.town : slingshot

the firehoses have a decent number of consumers, many of which don't identify themselves :)

skyblur.uk : one of the first apps ever to use constellation!

Projects

Sources for projects are at https://tangled.org/microcosm.blue/ (some github code still needs to be moved)

I think this is most of what i worked on this year:

Constellation : global lexicon-agnostic backlink index

Primary microcosm infrastructure

Indexed over 11 BILLION links!

Community forks implementing alternate storage backends

At least a half-dozen third-party self-hosted instances!

Slingshot

Firehose-listening atproto record cache and identity resolver

Created a popular XRPC endpoint for easily querying identities, com.bad-example.identity.resolveMiniDoc

Spacedust

Backlinks firehose, filterable by link subject

plc.wtf and experimental.plc.wtf

PLC mirror wrapping (with Allegedly) the official reference implementation

High-availability database and application architecture meeting baseline adversarial PLC fork requirements

Experimental endpoints including upstream op forwarding

Allegedly

PLC server tools for rapid backfill, command-line op tailing, weekly bundle exporting, and several configurations for wrapping the reference PLC server implementation.

UFOs API

Samples and statistics of atproto records by collection NSID

Hourly HyperLogLog sketches for accurate unique-user estimates that can be aggregated over arbitrary sets of NSIDs and arbitrary timescales

Simple CORS-friendly APIs to query the data

UFOs app

Top lexicons, all lexicons, various stats and info, available over a web UI for UFOs API

Public full-network firehoses

Free-to-use public alternatives to Bluesky-owned infrastructure.

Among the longest-running and I think the most widely used alternatives.

Canada relay -> Canada jetstream

France relay -> Germany jetstream

US-East jetstream (listens to bsky.network relay)

debug.hose.cam

In-browser debugger with various diagnostics for handles, repos, and PDSs.

compare.hose.cam

In-browser tool for comparing public atproto firehoses

repo-stream

Fast and robust atproto CAR file processing in rust

Bounded memory usage by dumping large repos to disk

spacedust notifications demo [needs repair]

Universal atproto webpush notifications via Spacedust

Pocket demo (+reflector) [demo offline]

Personal private data storage for atproto apps

who-am-i [retired]

One-click atproto login for microcosm demos

backlinks for atproto-browser [retired]

Forked atproto-browser.vercel.app to add backlinks (never merged)

everything-app demo [retired]

Global timeline of recent records from all lexicons via UFOs API

Simple rendering heuristics made a surprising number of record types automatically pretty legible.

cardinality-estimator-safe

Fork (and significant rewrite) of cloudflare's cardinality-estimator to avoid memory unsafety

backlinks data explorer [bit out of date]

d3.js-powered slicing of 1.2B atproto backlinks

live-updating post rendering

zero bluesky infrastructure

initial interaction counts via constellation

interaction count updates (live) via spacedust

deactivated account checker

In-browser tool for measuring the impact of a (now-fixed) relay bug on your own following list

microcosm.blue website

with real live code examples

good-first-issues bot

live-skeeted tangled issues having their hacktober good-first-issues tag

at://advent [WIP]

Collab with @baileytownsend.dev (mostly Bailey's efforts so far!) to create a daily challenge game for introducing new people to atproto

Writing

Can atproto scale down?

Adversarial PLC directory migration

Ramblings about running full-network indie relays

Post-mortem of microcosm's biggest incident in 2025

"weekly" updates

Open-source

[TODO: it's going to take forever to look them all up]

bluesky-social contributions

rsky contributions

(more than i have time to actually look up)

Architecture & ops

[TODO: i need to write more about this! probably in a separate post]

micro-ops: infra automation that's Good Enough For Now

microcosm has redundant infrastructure with automatic failover

public constellation backups on object storage: self-hoster bootstraping and main service disaster recovery

[TODO: summarize all incidents this year (there weren't many!). maybe a follow-up post]

Financial

Support received

AtmosphereConf travel support

Flights and hotels were covered by the conference

plc.wtf domain

Initial purchase donated by a community member

Bug bounties

reported memory-unsafety vulnerabilities in Cloudflare's cardinality-estimator rust crate (still unfixed 🙃 use my fork if you need hyper-log-logs)

mikrokosmos mini-pc

Backup low-power high-capacity home server donated by a community member

Upcloud credit

One-time credit supporting the first few months of operations for plc.directory in a HA configuration

Bluesky grant

General support for community projects

Github sponsors & ko-fi supporters

(Many of whom I still need to thank!)

The support that will truly keep this going long-term

[TODO: share total amounts and current monthly recurring]

Expenses

[TODO: collect all the actual numbers here]

Hardware

Raspberry Pi

2x Pi 5 16GB

1x Pi 5 8GB

NVME BASEs and HATs

SSDs

Power adapters

SD cards

RAM and SSD for micro-PC

Network switch

UPS power supply

Cloud servers

plc.wtf (upcloud)

Relays and Jetstream hosts (Servarica, OVH, Hetzner)

API gateways (DigitalOcean, Vultr)

Slingshot (OVH)

Slingshot dev machine (OVH)

Domains

microcosm.blue

hose.cam

plc.wtf

at-app.net

advent.codes

IETF 124 attendance

self-funded travel, hotel, meals, and full ticket

github sponsorships & ko-fi support

supported 10 atproto-community-oriented devs and projects

Blacksky

monthly contribution

Nice things that happened

I try to keep up with the Japanese atproto dev community, but sometimes I miss posts like this one:

Microcosm became a (tiny) part of IETF history:

Blacksky uses microcosm services:

A whole accessible dev intro to microcosm:

Microcosm code is hosted on tangled <3

People getting it

bryan specifically

This was a very short list, lots and lots of other nice things and nice people happened in 2025!!!

Cutting myself off here because there's lots more to get started on

Please consider supporting microcosm

Sponsor @uniphil on GitHub Sponsors

currently hacking on and hosting atproto projects: https://microcosm.blue art and transistors, small things that are nice

Support phil

The development and long-term upkeep of this community infrastructure relies on community support 💕