Senior Software Engineer – Voice

Are you looking to join a highly ambitious international technology startup and work on cutting edge technology? Do you want to build a career in technology but love to solve real life communications problems? Are you looking for a company that will invest time in your development, support your professional growth and listen to your ideas? If the answer is yes, we urge you to apply for a position with Telestax!

At Telestax, we connect an innovative community of customers, partners, and contributors to deliver trusted, high-performing technologies that solve business problems. Telestax is the leading CPaaS enabler for communications service providers and creator of the award-winning Restcomm API platform. Originating in the largest industry open source community, managed by Telestax, Restcomm has been tested by over 10,000 telecom developers and contains over 6 million lines of code.

Job Summary

Telestax is currently seeking a candidate to join our communications teams to develop, maintain, and manage real-time voice services that are processing calls, media, text-to-speech, speech-to-text, recordings, and conferencing. To take it to scale, you will be part of a team developing and maintaining a complex distributed platform with points of presence globally and will be concerned with availability, throughput, latency, media fidelity as well as real-time considerations.  At the core are cloud technologies that enable deployment and management of computing resources globally.

This team is responsible for deploying and designing distributed, scalable system real-time communications as we grow to reach five 9s uptime and horizontal scalability. Candidates in this space should have a strong desire to drive innovation by building feature rich, scalable systems that are conducive to evolution. Our products must handle continual core network traffic from Tier 1 operators, CPaaS companies, and large enterprises on a global scale. Travel for meeting your distributed team and conference events can happen over the course of your tenure at Telestax.

Primary Job Responsibilities

  • Collaborate with Product Managers, Architects, and Engineering leaders to define, architect and build new customer-facing features related to our Voice Services
  • Help drive the technical requirements, building, upgrade, and maintenance of our core voice services
  • Design, develop, and maintain SIP and real-time media infrastructure
  • Ensure that the Voice Services are highly available, stable, secure, performant, fault-tolerant, and scalable
  • Ensure that the Voice infrastructure is instrumented and monitored
  • Develop diagnostic and troubleshooting tools made to our customer support organization
  • Drive quality by writing unit, functional, performance, and capacity tests
  • Work closely with Site Reliability Engineers to ensure services are reliable, scalable, manageable, and supportable
  • Excel as an engineer and be a productive member of the team where leadership is a behavioral trait, not a title
  • Actively contribute to the adoption of strong software architecture, development best practices, and new technologies

Required Skills

  • Experience architecting, designing, developing, building, and operating a fault tolerant, highly available, reliable and performant SIP & Media Voice infrastructure in a telecom and/or cloud communications environment
  • Solid understanding of the Voice Session Handling and Media protocols including SIP, SDP, RTP, DTLS, RTCP, ICE, MGCP, and how they function together
  • You must be able to troubleshoot problems at a protocol level including experience with VoIP diagnosis tools like TCPDump or Wireshark
  • Extensive hands-on experience with Java and Java Microservices Framework and Application Servers such as Spring, Spring Boot, Akka, Vert.X, Tomcat, and JBoss
  • Experience operating and tuning Java server applications and knowledge about JVM internals (Memory & CPU Profiling)
  • Experience with Containers such as Docker
  • Experience with CI/CD practices (Pipelines, graceful shutdown, A/B upgrade, canary upgrades) and tools (Jenkins, Spinnaker, etc)
  • Automated testing experience (Junit/testing, SIPUnit, Mockito + Jmeter/
  • International experience (working in or with multicultural distributed environments)

Desirable Skills

  • Experience with load balancing, In memory data grid technologies (Infinispan, Redis)
  • Experience with Monitoring Voice and Media Services with tools such as Datadog, SIP3, Homer,
  • Experience with securing Voice and Media Services as part of DevSecOps
  • Experience with Cloud Environments such as AWS
  • Experience with Container Orchestration such Kubernetes, AWS ECS
  • Technical writing skills
  • Remote experience
  • You have worked in an Agile development environment
  • Ability to work in a fast-paced environment with fast moving team and changing requirements
  • Ability to work with independent thinkers who are highly technical and passionate


  • Rennes or Lannion, France
  • Remote Telestax Virtual Office

At Telestax you will enjoy working with real-time communications and cutting edge technology in a growing company and fast moving environment. You’ll also have the ability to work remotely and experience strong collaboration amongst small, focused, globally distributed teams for better customer impact. You’ll be part of a company that strives to build an inclusive culture where everyone is continuously seeking to improve both themselves and the system they operate in.


Telestax is proud to be an equal opportunity workplace and an affirmative action employer. We review applications for employment without regard to their race, color, religion, sex, sexual orientation, gender identity, national origin, ancestry, citizenship, age, uniformed services, genetic information, physical or mental disability, medical condition, marital status, or any other basis prohibited by law.

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