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
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 : 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!
Firehose-listening atproto record cache and identity resolver
Created a popular XRPC endpoint for easily querying identities,
com.bad-example.identity.resolveMiniDoc
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
PLC server tools for rapid backfill, command-line op tailing, weekly bundle exporting, and several configurations for wrapping the reference PLC server implementation.
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
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.
US-East jetstream (listens to bsky.network relay)
In-browser debugger with various diagnostics for handles, repos, and PDSs.
In-browser tool for comparing public atproto firehoses
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.
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
zero bluesky infrastructure
initial interaction counts via constellation
interaction count updates (live) via spacedust
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
live-skeeted tangled issues having their hacktober
good-first-issuestag
at://advent [WIP]
Collab with (mostly Bailey's efforts so far!) to create a daily challenge game for introducing new people to atproto
Writing
Post-mortem of microcosm's biggest incident in 2025
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:
The ATProto ecosystem at #IETF24 (Graze also mentioned!)
Blacksky uses microcosm services:
Blacksky is now using @bad-example.com's microcosm in two services. ko-fi.com/bad_example github.com/sponsors/uni... Support @bad-example.com!
A whole accessible dev intro to microcosm:
Microcosm code is hosted on tangled <3
People getting it
with @slices.network and @microcosm.blue Constellation offering easy indexing on the atmosphere, we’re getting close to a point where forks of the official bluesky client can augment it with non-trivial new features without running their own backend
bryan specifically
one of the best pieces of writing on atproto architecture. if you enjoyed the blog posts that @dustyweb.bsky.social and I exchanged, you should read this!
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
The development and long-term upkeep of this community infrastructure relies on community support 💕