Architecture

System Components

🗄️

User PDS

pds.bsky.social

⚙️

Stratos Service

API · OAuth · repo

📡

AppView

zone.stratos.feed.*

🔍

DID Resolver

PLC · did:web

📦

Blob Storage

disk or S3

🛢️

PostgreSQL

indexed records

Data Flow

User Enrollment

🧑

User

alice.bsky.social

⚙️

Stratos Service

stratos.example.com

🗄️

PDS

pds.bsky.social

🔑

Signing Key

secp256k1

✍️

Attestation

---

didalice.bsky.social

keysecp256k1

sig✓ by service

Record Creation

💻

Client App

createRecord

⚙️

Stratos Service

validate · sign · MST

🗄️

Actor Store

IPLD blocks · index

📌

User PDS

stub record

AppView Indexing

🔥

PDS Firehose

subscribeRepos

⚙️

Stratos Stream

subscribeRecords

🔄

Indexer

stratos-indexer

🛢️

PostgreSQL

stratos_post · boundaries

📡

AppView

zone.stratos.feed.*

Repository & MST Architecture

Stratos maintains a per-user Merkle Search Tree (MST) and signed commit chain compatible with the ATProto repo format. Every record write produces a signed commit that updates the MST root, enabling cryptographic verification of repository contents.

Layer	Contents
Signed Commit (v3)	did, version: 3, data (MST root CID), rev (TID), sig (P-256 signature)
MST	Sorted key-value tree mapping collection/rkey → record CID

Endpoint	Description
com.atproto.sync.getRecord	CAR with signed commit + MST inclusion proof + record block
zone.stratos.sync.getRepo	Full repo as a CAR file
zone.stratos.repo.importRepo	Import repo from CAR with CID integrity verification

Storage Architecture

Each enrolled user gets either an isolated SQLite database (default) or an isolated PostgreSQL schema.

SQLite layout:

/data/stratos/
├── service.sqlite              # Enrollment, OAuth sessions
├── blobs/                      # Blob storage (local provider)
│   ├── {did}/{cid}
│   ├── temp/{did}/{key}
│   └── quarantine/{did}/{cid}
└── actors/
    ├── ab/
    │   └── did:plc:abc123/
    │       └── stratos.sqlite  # Records, repo blocks
    └── cd/
        └── did:plc:cdef456/
            └── stratos.sqlite

Database Schema

stratos_record — record metadata

CREATE TABLE stratos_record (
    uri         TEXT PRIMARY KEY,
    cid         TEXT NOT NULL,
    collection  TEXT NOT NULL,
    rkey        TEXT NOT NULL,
    repoRev     TEXT,
    indexedAt   TEXT NOT NULL,
    takedownRef TEXT
);

stratos_seq — event sequencing for subscriptions

CREATE TABLE stratos_seq (
    seq   INTEGER PRIMARY KEY AUTOINCREMENT,
    did   TEXT NOT NULL,
    time  TEXT NOT NULL,
    rev   TEXT NOT NULL,
    event TEXT NOT NULL  -- JSON-encoded operation
);