Sr. Software Engineer - BE/Voip

About Our Client

Our client is making calls safe, useful, and human again.

Voice is the most human form of communication, yet it has become one of the least trusted. Spam, scams, and AI manipulation have eroded what was once a simple way to connect. Our client is changing that.

This is a pivotal moment for voice. As new threats and technologies accelerate, so does the demand for trusted voice communication. Our client is expanding globally and helping define what voice becomes next.

Join our client and help shape the future of voice: smarter, safer, and genuinely worth answering again.

About the Role

This role is part of a foundational team working at the intersection of backend systems, real-time voice infrastructure, and applied AI. You won't be maintaining legacy code or tweaking existing services—you'll be designing and building the backend platform from the ground up.

We're looking for engineers who get excited about greenfield architecture, want to make early decisions that shape how a product scales, and thrive when there's more whiteboard than runbook. As a Senior Full-Stack Software Engineer with a backend focus, you'll design and build the backend services and APIs that power our client’s next-generation voice products. This is a backend-first role with opportunities to work across the stack when it adds value.

The team builds a platform at the intersection of voice, telephony, and artificial intelligence. The work spans both audio intelligence, including deepfake detection and speaker verification, and conversational AI. The focus is on building resilient, scalable systems that integrate into operator networks and perform within real-time telephony environments.

What You'll Do

• Design and build backend services and APIs from scratch using TypeScript and Node.js
• Build real-time voice systems, including SIP/RTP media handling and STT/TTS pipelines with strict latency requirements
• Make foundational architecture decisions that will shape the platform for years to come
• Build systems that operate in real-time, high-availability voice environments
• Work with data stores, event streams, and cloud-based systems
• Collaborate with a distributed team across the United States and Europe using async-first working norms
• Work across the stack when needed, while maintaining a strong backend focus
• This is a hybrid role requiring three days per week in the Seattle office, with occasional travel as needed

What Success Looks Like

• 5–7 years of professional experience as a backend or backend-leaning full-stack engineer
• Strong fundamentals in backend architecture, API design, and data-driven systems
• Experience building reliable, production-ready applications and services
• Comfort with ambiguity—you know how to make good decisions without a playbook
• Interest in applied AI and voice technology
• Excellent communication and self-organization skills

What We're Looking For

Required:

• 5–7 years of professional software engineering experience
• Strong depth in TypeScript or Python, with a demonstrated ability to work meaningfully in other languages
• Experience with Node.js backend development and modern web-service patterns, including REST APIs, asynchronous processing, and event-driven systems
• Experience with VoIP or telephony technologies, including SIP, RTP, or WebRTC, or a strong interest in learning them
• Strong written and verbal communication—you write clear tickets and PRs and proactively flag blockers
• Pragmatic judgment—you make sensible tradeoffs between speed and perfection and can explain your reasoning
• Autonomy on well-scoped work—once you understand the goal, you drive the work to completion without needing hand-holding
• Honesty about what you don't know—you ask good questions early rather than allowing problems to surface late
• Reliable throughput—you ship consistently and follow through on commitments
• Active use of AI tooling—you leverage AI-assisted coding as a force multiplier and have a point of view on where it creates meaningful value

Preferred:

• Familiarity with DevOps fundamentals, including containers such as Docker, deployment workflows, CI/CD pipelines, and infrastructure configurations using Terraform, Helm, or similar tools
• Experience working with cloud infrastructure
• Carrier or B2B platform experience
• Experience with Databricks, Kafka, or streaming data pipelines
• Familiarity with AWS, including DynamoDB, S3, Kinesis, or EKS

About Our Client

Our client is making calls safe, useful, and human again.

Voice is the most human form of communication, yet it has become one of the least trusted. Spam, scams, and AI manipulation have eroded what was once a simple way to connect. Our client is changing that.

This is a pivotal moment for voice. As new threats and technologies accelerate, so does the demand for trusted voice communication. Our client is expanding globally and helping define what voice becomes next.

Join our client and help shape the future of voice: smarter, safer, and genuinely worth answering again.

About the Role

This role is part of a foundational team working at the intersection of backend systems, real-time voice infrastructure, and applied AI. You won't be maintaining legacy code or tweaking existing services—you'll be designing and building the backend platform from the ground up.

We're looking for engineers who get excited about greenfield architecture, want to make early decisions that shape how a product scales, and thrive when there's more whiteboard than runbook. As a Senior Full-Stack Software Engineer with a backend focus, you'll design and build the backend services and APIs that power our client’s next-generation voice products. This is a backend-first role with opportunities to work across the stack when it adds value.

The team builds a platform at the intersection of voice, telephony, and artificial intelligence. The work spans both audio intelligence, including deepfake detection and speaker verification, and conversational AI. The focus is on building resilient, scalable systems that integrate into operator networks and perform within real-time telephony environments.

What You'll Do

• Design and build backend services and APIs from scratch using TypeScript and Node.js
• Build real-time voice systems, including SIP/RTP media handling and STT/TTS pipelines with strict latency requirements
• Make foundational architecture decisions that will shape the platform for years to come
• Build systems that operate in real-time, high-availability voice environments
• Work with data stores, event streams, and cloud-based systems
• Collaborate with a distributed team across the United States and Europe using async-first working norms
• Work across the stack when needed, while maintaining a strong backend focus
• This is a hybrid role requiring three days per week in the Seattle office, with occasional travel as needed

What Success Looks Like

• 5–7 years of professional experience as a backend or backend-leaning full-stack engineer
• Strong fundamentals in backend architecture, API design, and data-driven systems
• Experience building reliable, production-ready applications and services
• Comfort with ambiguity—you know how to make good decisions without a playbook
• Interest in applied AI and voice technology
• Excellent communication and self-organization skills

What We're Looking For

Required:

• 5–7 years of professional software engineering experience
• Strong depth in TypeScript or Python, with a demonstrated ability to work meaningfully in other languages
• Experience with Node.js backend development and modern web-service patterns, including REST APIs, asynchronous processing, and event-driven systems
• Experience with VoIP or telephony technologies, including SIP, RTP, or WebRTC, or a strong interest in learning them
• Strong written and verbal communication—you write clear tickets and PRs and proactively flag blockers
• Pragmatic judgment—you make sensible tradeoffs between speed and perfection and can explain your reasoning
• Autonomy on well-scoped work—once you understand the goal, you drive the work to completion without needing hand-holding
• Honesty about what you don't know—you ask good questions early rather than allowing problems to surface late
• Reliable throughput—you ship consistently and follow through on commitments
• Active use of AI tooling—you leverage AI-assisted coding as a force multiplier and have a point of view on where it creates meaningful value

Preferred:

• Familiarity with DevOps fundamentals, including containers such as Docker, deployment workflows, CI/CD pipelines, and infrastructure configurations using Terraform, Helm, or similar tools
• Experience working with cloud infrastructure
• Carrier or B2B platform experience
• Experience with Databricks, Kafka, or streaming data pipelines
• Familiarity with AWS, including DynamoDB, S3, Kinesis, or EKS