Introduction

Stratos is a private permissioned data layer for ATProtocol. It keeps private records out of public purview, publishes enrollment metadata back to the PDS for discovery, and lets downstream apps serve boundary-filtered content without inventing a separate identity model.

What Problem Does It Solve?

ATProtocol is designed for open, public social data. Every record on a PDS is visible to anyone who knows the AT-URI. Stratos adds a permissioned layer on top: users can create posts that are only visible to members of specific communities, without leaving the AT Protocol identity and tooling ecosystem.

How It Works

🧑

User

alice.bsky.social

⚙️

Stratos Service

stratos.example.com

🗄️

PDS

pds.bsky.social

🔄

Indexer

stratos-indexer

🛢️

PostgreSQL

appview database

📡

AppView

zone.stratos.feed.*

💻

Client App

your application

1. A user enrolls with a Stratos service via OAuth. The service writes a zone.stratos.actor.enrollment record to the user's PDS.
2. The user creates private records by calling the Stratos XRPC API. Records are stored in the user's per-actor repo on Stratos, not on the PDS. A lightweight stub record is written to the PDS with a source field pointing back to Stratos.
3. A standalone indexer subscribes to the PDS firehose (to discover enrollments) and to each user's subscribeRecords stream (to index records with their boundary metadata).
4. An AppView queries the indexed PostgreSQL tables. When a viewer requests a feed, the AppView filters posts to only those whose boundaries overlap with the viewer's enrolled boundaries.

Repository Packages

Package	Description
stratos-core	Domain logic, storage interfaces, schema, validation, MST commit builder
stratos-service	HTTP/XRPC service, OAuth enrollment, repo CRUD, sync export, adapters
stratos-client	Discovery, routing, verification, and OAuth scope helpers
stratos-indexer	Standalone indexer consuming PDS + Stratos streams into AppView PostgreSQL
webapp	Svelte demo client for enrollment and private posting

Next Steps

• Read Core Concepts to understand boundaries, enrollment, and hydration.
• Follow the Client Integration Guide to add Stratos to your app.
• See the Operator Guide to deploy a Stratos service.
• Explore the Architecture for deep technical detail.