BitsPath
Carrier-grade CPaaS built from scratch with a pure Rust PBX core
The Challenge
What we were solving.
Building a communications platform that could compete with Twilio and MessageBird required carrier-grade reliability from day one. Off-the-shelf PBX solutions like Asterisk and FreeSWITCH carried too much legacy baggage and couldn't meet our latency and concurrency requirements.
The platform needed to handle voice (SIP/RTP/SRTP), WebRTC browser calling, SMS routing across multiple operators, email delivery with high inbox rates, and WhatsApp Business API -- all through a unified API surface.
SMS delivery in Bangladesh requires SIGTRAN/SS7 protocol support for direct operator interconnection. No existing open-source library provided this in a language suitable for high-concurrency, low-latency processing.
What We Built
Technical architecture.
A pure Rust PBX engine spanning 50,000 lines of code. Rust was chosen for its zero-cost abstractions, memory safety guarantees, and predictable latency characteristics -- critical for real-time voice processing. The PBX handles SIP registration, call routing, RTP/SRTP media relay, and WebRTC gateway functionality.
A 13-service CPaaS architecture built on .NET 10 surrounds the Rust PBX core. Services cover SMS routing (with smart operator selection based on cost and deliverability), email delivery (98.5% inbox rate), WhatsApp Business API, campaign management, and CRM integration.
214 API endpoints expose the full platform capability through a REST API. The email service includes a GrapeJS-based drag-and-drop template builder. SMS routing intelligently selects operators based on destination network, cost, and historical delivery rates.
A SIGTRAN/SS7 SMS gateway enables direct operator interconnection for bulk SMS delivery, bypassing aggregators and their associated costs and latency.
Key Numbers
By the numbers.
Technology Stack
Built with.
Outcome
Business results.
The platform delivers carrier-grade voice quality with sub-50ms jitter and 99.95% uptime. The Rust PBX handles thousands of concurrent calls with predictable resource consumption.
Email delivery achieves 98.5% inbox placement rate through proper DKIM/SPF/DMARC configuration, IP warming strategies, and content analysis.
Direct operator interconnection via SIGTRAN/SS7 reduced SMS delivery costs by 40% compared to aggregator-based routing while improving delivery speed and reliability.
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