Senior Software Engineer - Core VoIP (SIP Backbone)

About Practice by Numbers:

Practice by Numbers is a leading dental practice management SaaS platform serving over

1,500 dental practices across North America, providing practice management, VOIP telephony,

payments, and advanced analytics. The platform is evolving into an AIfirst product, adding

conversational automation and intelligent communication workflows for patients and front-office

teams.

About the Role:

This role owns the design and implementation of the core VoIP/SIP telephony backbone for

PBN, including SIP routing, media handling, scalability, and reliability. The engineer will architect

and build Golangbased SIP services and control planes on top of opensource components

such as Kamailio (or similar SIP server), FreeSWITCH/OpenSIPS, and related media/RTP

proxies.

This role reports to the Engineering India Head.

Location: Kolkata / Gurugram, India

Work Mode: In-office

Employment type: Full-time

Key Responsibilities:

- Design and implement a carriergrade SIP/VoIP core using components like

Kamailio/OpenSIPS for SIP signaling and FreeSWITCH or similar for media and

application services.

- Build Golangbased SIP services (registrar, SBClike components, routing logic,

monitoring daemons) and internal APIs to control routing, policies, and provisioning.

- Configure and operate SIP load balancing, failover, and highavailability setups

(multinode SIP proxies, distributed media servers, RTP proxies).

- Implement and maintain dial plans, leastcost routing, DID management, class4/class5

style switching logic, and integration with upstream carriers and PSTN gateways.

- Own security and robustness of the VoIP stack: TLS/SRTP, authentication/authorization,

rate limiting, fraud detection hooks, and abuse controls.

- Integrate the telephony backbone with PBN's SaaS platform (user accounts, billing,

analytics, AI/automation flows) via welldefined internal APIs and webhooks.

- Define monitoring, alerting, logging, and capacity planning for SIP signaling, RTP/media,

and VoIP quality (MOS, jitter, packet loss).

- Collaborate with product and operations to translate business requirements (IVRs, call

queues, routing rules, AI agents) into resilient VoIP and backend designs.

Required Qualifications:

- 710 years of software development experience with at least 45 years building or

operating largescale VoIP/SIP systems.

- Strong Golang skills, including building highperformance networked services,

concurrent processing, and productiongrade APIs.

- Handson experience with at least one opensource SIP server such as

Kamailio/OpenSIPS and one media/application server such as FreeSWITCH (or

Asterisk), including configuration, routing logic, and troubleshooting.

- Deep understanding of SIP, RTP, SDP, NAT traversal, registrar/registrations, B2BUA vs

proxy behavior, and SBC concepts.

- Proven ability to design and run highly available telephony backbones: clustering, health

checks, load balancing, and graceful failover.

- Strong Linux and networking fundamentals (iptables, firewalls, TCP/UDP, QoS), and

comfort debugging issues at packetlevel using tools like tcpdump/wireshark.

- Experience integrating VoIP platforms with RESTful backends, databases (PostgreSQL

or MariaDB/MySQL), and message queues for control and billing workflows.

Nice to Have:

- Experience with WebRTC, SIP over WebSockets, and browser/mobile softphone

integrations.

- Familiarity with VoIP billing, rating engines, CDR processing, and reseller hierarchies

(class4/class5 softswitch products or similar).

- Cloudnative deployment of VoIP stacks (containerized Kamailio/FreeSWITCH clusters

on AWS/GCP, Kubernetes, service meshes).

- Prior work building call center or CPaaSstyle platforms, including programmable IVRs,

queues, and analytics.

Success Indicators:

- A robust, observable VoIP backbone that can sustain high call volumes with low failure

rates and predictable call quality across geographies.

- Rapid rollout of new telephony features (IVRs, routing rules, AI agents) through clean

APIs and configurationdriven behavior rather than manual changes.

- Demonstrated reduction in telephony incidents and MTTR through automation, strong

monitoring, and clear runbooks.

Preferred Educational Background:

- Bachelor's/Master's degree from IITs/IIMs or equivalent top rated institutions

- Proper certifications on the subject