Senior VoIP / Telecom Engineer to Build Twilio-Scale Dialer, Routing & LCR Platform (FreeSWITCH)

Senior VoIP / Telecom Engineer to Build Twilio-Scale Dialer, Routing & LCR Platform (FreeSWITCH)

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## **Job Description**

We are building a **Twilio-scale telecom execution and call-routing ecosystem** focused on **ultra-high volume**, **extreme cost efficiency**, and **enterprise-grade reliability**.

This platform is intended to support millions of calls per day, across multiple carriers, with dynamic routing, full observability, and compliance-by-design.

This is **not** a single application. It is a **distributed telecom system** made up of multiple independent services that communicate through APIs, events, and shared data contracts.

We are looking for a **senior engineer or architect** who has built real VoIP systems in production and understands how these pieces work together at scale.

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## **High-Level Architecture (Conceptual Flow)**

**[ Lead / Trigger Source ]**
? **Calldialer (Outbound Execution Layer)**
? **LCRHV (Carrier & Cost Routing Engine)**
? **FreeSWITCH Cluster (SIP + RTP Media)**
? **CallRouter (Buyer & Revenue Routing)**
? **DataManager (Central Data + Compliance Layer)**

Each system is independently deployable, horizontally scalable, and fault-tolerant.

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## **Core Systems You’ll Work On**

### **1) Calldialer — Outbound Dialer & Execution Engine**

Calldialer is our replacement for a traditional “Press-1” dialer.

Responsibilities:

* Built on **FreeSWITCH**
* Executes outbound calls at massive scale
* Handles:

* Dial pacing and concurrency control
* Audio playback
* DTMF / Press-1 detection
* Call retries, failure handling, and scheduling rules
* Publishes real-time call lifecycle events
* Designed to scale horizontally across multiple FreeSWITCH nodes

This system is optimized for **throughput, predictability, and recoverability**, not UI polish.

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### **2) LCRHV — Least-Cost High-Volume Routing Engine**

LCRHV is the **decision engine** that determines *how* a call leaves the system.

Responsibilities:

* Selects optimal SIP carrier per call
* Considers:

* Cost per route
* Carrier health
* Failure rates
* Dynamic degradation and failover
* Must operate with **extremely low latency** and **very high concurrency**
* Prevents carrier exhaustion or blacklisting
* Provides routing telemetry to downstream systems

This is the **economic brain** of the platform.

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### **3) FreeSWITCH Cluster — SIP & Media Layer**

The FreeSWITCH layer handles **call signaling and RTP media**.

Responsibilities:

* SIP signaling
* RTP media handling
* ESL / event socket integration
* Horizontal scaling across nodes
* Media isolation and fault containment
* Emits detailed call detail records (CDRs)

You should understand how to:

* Separate signaling from media load
* Scale RTP safely
* Recover from partial failures without dropping the system

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### **4) CallRouter — Call Distribution & Monetization Platform**

CallRouter is a **Ringba-style routing system** that determines *where* calls go after they connect.

Responsibilities:

* Routes inbound calls to buyers or destinations
* Supports:

* Rule-based routing
* Revenue-based optimization
* Buyer caps, schedules, and throttles
* Handles:

* Webhooks and postbacks
* Buyer and affiliate attribution
* Call outcome tracking
* Provides operational visibility for routing decisions

This layer directly controls **monetization efficiency**.

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### **5) DataManager — Central Data, Analytics & Compliance Layer**

DataManager is the **system of record**.

Responsibilities:

* Central SQL data warehouse
* Stores:

* Call detail records
* Routing decisions
* Buyer performance metrics
* Suppression lists
* Consent evidence
* Audit logs
* Feeds analytics, reporting, and segmentation
* Enforces compliance logic across the platform

All systems read/write through defined schemas and contracts.

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## **Infrastructure Expectations**

* Linux-based servers
* API-driven services
* Event-driven communication where possible
* Clear separation of responsibilities
* Observability from day one:

* Logs
* Metrics
* Alerts
* Repeatable deploy, rollback, and debugging processes

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## **Required Experience**

* **FreeSWITCH** (dialplan, SIP, ESL/event socket)
* Strong **VoIP/SIP** fundamentals (RTP, codecs, NAT, failover)
* High-volume distributed systems
* Backend API development
* SQL schema design and performance tuning
* Linux + production DevOps

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## **Strongly Preferred**

* Ringba / Retreaver-style routing experience
* VICIdial exposure
* Least-cost routing systems
* Experience using **Cursor, Antigravity, or other agentic coding tools** to ship faster and more accurately
* Ability to work autonomously and think architecturally

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## **Compliance**

This platform must support **auditability, suppression logic, and compliance-by-design**.
We do not cut corners.

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## **What Success Looks Like**

* Live carrier calls flowing end-to-end
* Stable routing under heavy load
* Clean, extensible data models
* Documented architecture and runbooks
* Systems that can be scaled confidently without fear

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## **To Apply**

Include:

1. Your FreeSWITCH or VoIP scaling experience
2. Any routing or LCR systems you’ve built
3. How you use Cursor or AI coding tools in real projects

Hourly or fixed-bid depending on experience.

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