Enterprise-grade workforce logistics and scheduling engine. Built by Fastcomcorp LLC, designed to securely manage and dispatch enterprise workforces at massive scale.
- Why Casin?
- Core Features
- The Split-Brain Architecture
- Quick Start
- Ports & Networking
- Documentation
- Security & Fuzz Testing
- License & Contributing
Traditional scheduling platforms often rely on synchronous HTTP polling, which can lead to severe performance bottlenecks during concurrency spikes—such as thousands of employees engaging in shift bidding simultaneously. Casin JMAP Server overcomes this scaling limitation by separating the mathematical scheduling logic from real-time communication using a modern Split-Brain Architecture. This event-driven approach provides strict immunity to double-booking and enables seamless, real-time schedule synchronization across highly distributed workforces.
- Mathematical Double-Booking Protection: Utilizes PostgreSQL GiST Range Types to physically prevent double-booking at the database level.
- JMAP Native (RFC 8620): Highly optimized JSON payloads reduce bandwidth by up to 80% compared to REST.
- 100% Market Sync Coverage: Silently syncs shifts directly to employees' personal Apple iCloud, Google Workspace, and Microsoft 365 calendars.
- ArcRTC Offline Sync: If field workers lose cell service, schedules sync locally via proprietary, encrypted ArcRTC UDP mesh networks.
- Massive Concurrency: The Elixir cluster easily manages 300,000+ simultaneous WebSockets.
One of the most critical failures of legacy scheduling software is losing sync when field workers enter dead zones (e.g., hospital basements, rural logistics routes). Casin solves this using the proprietary ArcRTC Protocol.
If a worker loses cellular connection:
- Signaling: Before losing service, the Elixir cluster provisions ArcRTC connection parameters to all workers on the same shift.
- Mesh Network: Devices automatically discover each other via Local Wi-Fi Direct or Bluetooth and form an encrypted UDP mesh network.
- Peer-to-Peer Sync: Shift changes, clock-ins, and task completions are synced directly from phone-to-phone.
- Reconciliation: The moment any single device in the mesh regains cellular service, it acts as a relay, pushing the entire mesh's state back to the Casin Server for PostgreSQL reconciliation.
graph TD
A[Mobile App / Web UI] -->|HTTPS JMAP JSON| B(Rust Axum API)
B -->|GiST Constraint Check| C[(PostgreSQL)]
B -->|Publish Shift Change| D{NATS JetStream}
D -->|Consume Event| E[Elixir Phoenix Cluster]
E -->|WebSocket Push| A
E -->|Oban Rate-Limited Queue| F[Google/Microsoft/Apple APIs]
- Rust (Axum): The Ironclad Gateway. Handles JMAP parsing, JWT authentication, and executes safe SQL queries.
- Elixir (Phoenix/Oban): The Realtime Router. Manages all WebSockets, WebPush notifications, and API syncs to external calendars.
- NATS JetStream: The Firehose. Lightning-fast internal messaging connecting Rust and Elixir.
To boot the entire Casin stack for local development, ensure you have Rust, and Elixir installed.
# Clone the repository
git clone https://github.com/fastcomcorp/casin-jmap-server.git
cd casin-jmap-server
# Run the unified boot script
./start.shThe script will automatically boot the Rust and Elixir backends in the background and connect to your local PostgreSQL and NATS instances.
For production deployments, Casin requires the following minimum specifications and versions to handle the intended scale:
- PostgreSQL:
>= 15.0(Required for advanced GiST Exclusion Constraint features) - NATS JetStream:
>= 2.9.0(Required for guaranteed delivery semantics) - Rust:
>= 1.70 - Elixir:
>= 1.15(Erlang/OTP 25+)
To support 10,000+ concurrent users with sub-millisecond response times, we recommend the following minimum hardware per node:
- Rust API Gateway: 2 vCPU, 4GB RAM
- Elixir WebSocket Cluster: 4 vCPU, 8GB RAM (Scales horizontally)
- PostgreSQL Database: 4 vCPU, 16GB RAM, SSD Storage (Critical for GiST index performance)
When deploying to AWS or configuring local firewalls, ensure the following ports are accounted for:
| Service | Port | Protocol | Scope | Description |
|---|---|---|---|---|
| Rust Axum (JMAP) | 3000 |
TCP / HTTPS | Public | Main API Gateway for mobile apps (Requires JWT). |
| Elixir Phoenix | 4000 |
TCP / WSS | Public | WebSocket secure connections for real-time sync. |
| ArcRTC Relay | 50000-60000 |
UDP | Public | Dynamic port range for ArcRTC media transport and mesh signaling. |
| PostgreSQL | 5432 |
TCP | Internal VPC | Database storage and GiST logic. |
| NATS JetStream | 4222 |
TCP | Internal VPC | Internal messaging firehose. |
| Elixir libcluster | 45892 |
UDP Multicast | Internal VPC | Mesh networking protocol for Elixir nodes. |
Caution
Never expose 4222, 5432, or 45892 to the public internet. They must remain isolated within your private cloud subnet.
This server is mathematically hardened against Denial of Service (DoS) attacks.
- Fuzz Tested: The JSON parsers have been blasted with malformed data, deep-nesting bombs, and null-byte injections to mathematically prove they will not crash.
- Erlang Atom Exhaustion: The Elixir NATS consumer uses strict string-key parsing (
keys: :strings) to prevent memory exhaustion attacks. - Encrypted in Transit: All data hops mandate TLS 1.3, DTLS (for WebRTC), and strictly rotated OAuth 2.0 tokens.
Comprehensive documentation for developers and DevOps engineers can be found in the docs/ directory:
- Developer Handbook - Architecture Overview & Troubleshooting.
- ArcRTC Protocol - WebRTC Offline Mesh Sync Specification.
- Billion User Architecture - Roadmap for Citus Sharding.
Copyright (c) 2026 Fastcomcorp, LLC. All rights reserved.
This project is open-source and licensed under the GNU Affero General Public License v3.0 (AGPL-3.0). See the LICENSE file for the full legal text.
For enterprise usage without the AGPL v3 open-source restrictions, Commercial Licenses are available. If you wish to integrate the Casin JMAP Server into your proprietary backend without being forced to open-source your own code, please contact licensing@fastcomcorp.com for commercial pricing.
We welcome community contributions! However, to protect the intellectual property of this project, all contributors must sign a Contributor License Agreement (CLA) before any code can be accepted or merged. Please see CONTRIBUTING.md for details.
The Casin JMAP Server stands on the shoulders of giants. We would like to extend our deepest gratitude to the open-source community and the maintainers of the following critical libraries that made this project possible.
- Tokio: The asynchronous runtime that powers our extreme concurrency.
- Axum: The ergonomic and lightning-fast web framework routing our JMAP payloads.
- SQLx: For compile-time checked, asynchronous PostgreSQL database access.
- async-nats: The official NATS client for Rust, enabling our split-brain architecture.
- Phoenix Framework: The unparalleled web framework managing our WebSocket infrastructure.
- Oban: The robust job processing queue ensuring our Google/Microsoft/Apple API syncs are strictly rate-limited and never lost.
- libcluster: The backbone of our distributed Elixir node mesh network.
- Gnat: The high-performance NATS client for Elixir.