Strata

Inside the route

1. The server authenticates the upgrade. The client sends ?token=… on the WebSocket URL. The server compares it with STRATA_TOKEN in constant time. It returns HTTP 403 for an invalid token.
2. One store actor owns document state. The actor keeps documents keyed by ID, merges ORMap state, and coordinates persistence. beryl manages each socket and doc:<id> topic join.
3. Join with a snapshot; continue with deltas. A join or reconnect receives a snapshot. Each later delta frame contains encoded ORMap state.
4. The server merges, writes, then broadcasts. The server merges state with lattice_crdt and writes it to shelf. It then uses beryl.broadcast_from to send the state to the other sockets.
5. Presence is separate from the document. Cursors, selections, names, and colors live in a per-document add-wins set and vanish with the socket.
6. Client and server share one codec. strata_protocol compiles for Erlang and JavaScript, so frames cannot drift between the two ends.

When to use Strata instead of beryl

beryl provides the transport: typed real-time channels, presence, and a Phoenix-Channels-compatible wire format. Its collab_docs example shows how to build a CRDT application directly. Strata packages that pattern as a typed stack with a server, client, document schemas, component contracts, transports, persistent storage, and an admin interface.

Concern	beryl + collab_docs	Strata
Wire protocol	Two ad-hoc events per app	Versioned v0 envelope shared by client and server
Sync model	Whole-state merge on every edit	Snapshot on join; encoded ORMap state on later edits
Persistence	In-memory Dict, lost on restart	shelf ETS + DETS with periodic flush and schema-validated decoders
Runtime model	Application-owned example state	Supervised channels plus a durable document Store actor
Auth	HMAC token in the join payload (example code)	Shared secret checked on the WebSocket upgrade; JWT slots in later
Client	None; each application implements a client	strata_client, transport-agnostic, Erlang and JavaScript
Admin	None	Read-only Lustre SPA at /admin: docs, sizes, sockets, presence
Configuration	Hard-coded in the example	StrataConfig: rate limits, persistence, static assets

The stack

Package	Target	Purpose
strata_protocol	Erlang · JS	Frame types and JSON codecs
strata_document	Erlang · JS	Typed CRDT fields, records, and document IDs
strata_server	Erlang	mist + beryl + shelf server runtime
strata_client	Erlang · JS	Sans-IO client state machine
strata_component	Erlang · JS	Headless components, typed ports, and bindings
strata_transport	JS	Browser WebSocket transport
strata_transport_gun	Erlang	Gun-backed transport
strata_admin	JS	Read-only Lustre admin SPA

Built on beryl, lattice, shelf, and mist. Strata packages are not on Hex. Build them from source.

Release state: pre-1.0

Works today

• Single-node server, delta sync, presence, persistence across restarts
• Typed documents, composition, and headless component contracts
• The full v0 frame set on both targets
• Reconnect, demonstrated in the bundled examples
• Read-only admin, per-socket rate limits
• Target-specific unit tests and Playwright tests for the examples

May change

• Wire protocol (versioned, no compatibility promise yet)
• Public package APIs
• On-disk storage format

Deferred, tracked

• JWT and multi-tenant auth
• Chunked snapshots
• Multi-node clustering
• DotContext garbage collection

Full limitations · Roadmap

Run it locally

git clone https://github.com/tylerbutler/strata.git
cd strata
mise install && just deps && just build-all
just example kanban        # http://localhost:8000 in two tabs

Quick Start Source on GitHub