Senior Full Stack Engineer (Realtime & Voice) Customer Experience Platform

Full Stack Engineer · Senior · Full Time · Remote

Spain - Remote · RemoteUSD 160k – 220k4d ago
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Role

What you'll do.

Lead the real-time voice and chat infrastructure for Hopper's HTS Assist, an agentic AI assistant serving enterprise travel brands at scale. As a Senior Full Stack Engineer, you'll own the voice channel end-to-end—from telephony and CPaaS integrations through speech-to-text/text-to-speech pipelines—while building across React/TypeScript frontends, Scala and Python backends, and GCP cloud infrastructure. This is a high-impact role requiring 6+ years of production engineering experience with genuine full-stack capabilities, hands-on expertise in real-time systems, and the ability to ship iteratively in a lean, senior-driven team.

Responsibilities

  • Own voice channel end-to-end: Design, build, and maintain the complete voice infrastructure including telephony integrations (Twilio, Amazon Connect), CPaaS platform orchestration, streaming speech-to-text (Whisper, Deepgram) and text-to-speech pipelines (ElevenLabs), real-time model orchestration, and latency/quality budgets to ensure sub-second response times in production.
  • Build and ship full-stack product features: Develop features across the entire technology stack including web chat interfaces in React/TypeScript, backend services and APIs in Scala and Python, cloud infrastructure provisioning on GCP, and database layer design to support multi-tenant enterprise scale.
  • Architect for multi-tenant scale and configuration: Design systems that serve multiple travel partners through a single codebase with configuration-driven customization rather than code forks, enabling rapid partner onboarding and reducing maintenance overhead across enterprise clients.
  • Implement safety, compliance, and data protection: Build enterprise-grade guardrails, content filtering logic, PII redaction integration points, compliance plumbing, and audit trails that enterprise partners require for regulated financial and customer service operations.
  • Maintain revenue-critical system reliability: Establish comprehensive observability through logging, metrics, and distributed tracing; configure intelligent alerting; participate in on-call rotations; respond to production incidents; and track SLA compliance for mission-critical customer service workflows.
  • Enable partner go-live and deployments: Build platform capabilities and configuration interfaces that forward-deployed engineers use to integrate customer telephony systems, manage partner-specific workflows, and orchestrate successful production launches with minimal engineering overhead.
  • Raise engineering standards and mentorship: Conduct thorough code reviews and architecture reviews across the team, mentor junior engineers, establish best practices for real-time systems and voice infrastructure, and continuously improve code quality and architectural decisions through peer feedback.

Qualifications

What we look for.

Technical

  • Full-stack production systems ownership

    Demonstrated ability to own and operate complete systems from frontend through infrastructure, with accountability for performance, reliability, and user experience in production environments serving millions of requests.

  • Real-time systems expertise

    Hands-on experience building low-latency, high-throughput systems such as voice applications, WebRTC/SIP implementations, streaming media platforms, video conferencing, or comparable real-time products with strict latency budgets.

  • Modern frontend development

    Strong proficiency in React and TypeScript including component architecture, state management, performance optimization, accessibility standards, and building responsive interfaces that handle real-time data updates gracefully.

  • Backend systems and API design

    Production expertise in Scala or another JVM language (Java, Kotlin) and/or Python with deep understanding of REST API design, microservices patterns, event-driven architectures, database optimization, and scalable service design.

  • Cloud infrastructure and DevOps

    Hands-on experience with GCP (preferred) or AWS services including compute, networking, storage, observability tools (Cloud Logging, Cloud Monitoring), CI/CD pipelines, infrastructure-as-code, and containerization with Docker/Kubernetes.

  • Streaming and real-time data pipelines

    Experience designing and maintaining data pipelines that handle streaming inputs such as audio, video, or other high-frequency event streams, including understanding of buffering, backpressure, and end-to-end latency management.

Education

  • Computer Science or equivalent

    Bachelor's degree in Computer Science, Software Engineering, or equivalent professional experience demonstrating core computer science fundamentals including algorithms, data structures, and systems thinking.

Experience

  • Senior-level engineering experience

    Minimum 6+ years of professional software engineering experience with demonstrated senior-level ownership of production systems, including architectural decisions, on-call responsibility, incident response, and cross-team technical leadership.

  • Production systems reliability

    Proven track record building and maintaining systems with strict SLA requirements, implementing observability and monitoring, managing on-call rotations, conducting incident postmortems, and reducing mean-time-to-recovery (MTTR).

  • API and microservices architecture

    Significant experience designing, implementing, and scaling RESTful APIs, microservices architectures, or event-driven systems with consideration for backward compatibility, versioning, and multi-client support.

  • Complex problem decomposition

    Ability to break down complex technical challenges into manageable components, evaluate tradeoff spaces, prioritize pragmatically, and communicate architectural and technical decisions clearly across engineering, product, design, and operations teams.

Skills

Required

  • React and TypeScript

    Production-grade proficiency building responsive, performant web interfaces with modern React patterns, TypeScript type safety, and real-time data synchronization.

  • Scala or JVM languages

    Deep production experience with Scala, Java, or Kotlin for building scalable backend services with strong typing, immutability, and functional programming concepts.

  • Python

    Proficiency in Python for backend services, data processing, machine learning integrations, and scripting, with understanding of async frameworks and performance considerations.

  • RESTful API design

    Expertise in designing and implementing scalable, maintainable REST APIs with proper HTTP semantics, versioning strategies, error handling, and documentation.

  • GCP or AWS cloud platforms

    Hands-on experience with cloud infrastructure including compute instances, networking, managed services, databases, and observability tooling in GCP (preferred) or AWS environments.

  • Microservices and distributed systems

    Understanding of microservices patterns, service-to-service communication, eventual consistency, distributed tracing, and troubleshooting across multiple services.

  • Observability and monitoring

    Experience implementing comprehensive logging, metrics collection, distributed tracing, and alerting systems to maintain visibility and incident response capabilities.

  • AI coding tools

    Proficiency using GitHub Copilot, Claude, ChatGPT, or similar AI-assisted development tools as part of daily workflow, with strong judgment to review, test, and own all generated code.

Preferred

  • Conversational AI and LLM orchestration

    Nice to have

    Experience building chat systems, voice applications, or real-time AI applications with knowledge of prompt engineering, context management, and orchestrating multiple LLM calls for complex workflows.

  • Speech technologies and voice processing

    Nice to have

    Hands-on experience with speech-to-text engines (Whisper, Deepgram), text-to-speech synthesis (ElevenLabs), voice activity detection, speaker identification, or audio signal processing.

  • Cloud telephony and CPaaS platforms

    Nice to have

    Working knowledge of Twilio, Amazon Connect, Genesys, LiveKit, or similar cloud communications platforms including SIP, WebRTC, call routing, and media handling.

  • WebRTC and real-time communication

    Nice to have

    Experience building peer-to-peer communication systems, video conferencing, or WebRTC applications with understanding of codec negotiation, ICE candidates, and media stream optimization.

  • Customer service and contact center tools

    Nice to have

    Experience building or integrating with customer service platforms, CRM systems, contact center solutions, or workflow automation tools serving enterprise customers.

  • Travel industry technology

    Nice to have

    Familiarity with travel-specific systems such as Global Distribution Systems (GDS), Property Management Systems (PMS), Passenger Service Systems (PSS), or Common Reservation Systems (CRS).

  • Event-driven architecture

    Nice to have

    Experience designing systems with event streaming platforms (Kafka, Pub/Sub), event sourcing, and asynchronous processing patterns for high-throughput, loosely-coupled services.

  • Multi-tenant system design

    Nice to have

    Experience building multi-tenant SaaS applications with consideration for data isolation, configuration management, scalability per tenant, and compliance boundaries.

Tech stack

Languages

TypeScriptScalaPythonJavaScript

Frameworks

ReactPlay Framework or AkkaFastAPI or DjangogRPC

Databases

Cloud Spanner or PostgreSQLCloud Datastore or FirestoreRedis

Tools

TwilioAmazon ConnectWhisper (OpenAI)DeepgramElevenLabsDocker and KubernetesCloud Logging and Cloud MonitoringDatadog or New RelicGitHub or GitLab

Other

WebRTCSIP (Session Initiation Protocol)gRPC streamingPub/Sub (Google Cloud Pub/Sub or Apache Kafka)OpenAI Realtime API

Compensation

Pay and benefits.

Base·USD 160,000 – 220,000

Equity·Stock options

Full posting

Original listing.

About the Role

HTS Assist is Hopper's agentic AI assistant for travel, resolving flight changes, cancellations, refunds, and bookings over chat and voice for some of the world's largest travel brands. We're looking for a senior full stack engineer to anchor this product, owning the realtime and voice layer end to end while building across React/TypeScript front ends, Scala and Python services, and cloud infrastructure. The team is lean and senior, ownership is broad, and the path from your code to a traveler's phone call is short.

What would your day-to-day look like

  • Own the voice channel end to end, including telephony and CPaaS integrations (e.g., Twilio, Amazon Connect), streaming speech-to-text and text-to-speech pipelines, realtime model orchestration, and latency and quality budgets

  • Build product features across the stack, including web chat front ends in React/TypeScript, backend services in Scala and Python, and infrastructure on GCP

  • Design for multi-tenant scale, with one codebase serving many partners through configuration rather than forks

  • Build the safety and compliance plumbing enterprise partners audit, including guardrails, content filtering, and PII redaction integration points

  • Keep revenue-critical deployments healthy through observability, alerting, incident response, and SLA performance

  • Build the platform capabilities forward-deployed engineers configure for partner telephony integrations and go-lives

  • Raise the engineering bar through code review, architecture reviews, and mentoring

An ideal candidate has

  • 6+ years of software engineering experience, with senior-level ownership of production systems and genuine full-stack range

  • Hands-on realtime systems experience, such as voice applications, WebRTC/SIP, streaming media, or comparable low-latency products

  • Strength in a modern front end (React, TypeScript) and depth on the backend (Scala or another JVM language, and/or Python), along with cloud infrastructure experience on GCP or AWS

  • A track record designing, building, and maintaining RESTful APIs, microservices, or event-driven systems

  • Familiarity using AI coding tools as a standard part of their workflow, with the judgment to review, correct, and own everything that ships

  • An operable-systems mindset, covering SLAs, observability, on-call rotations, and rollback plans

  • The ability to break down complex problems, make pragmatic tradeoffs, and ship iteratively, backed by strong communication across product, design, and operations

  • Bonus points for conversational AI or LLM orchestration experience, including speech technologies such as Deepgram, ElevenLabs, Whisper, or OpenAI Realtime

  • Bonus points for working knowledge of cloud telephony or CPaaS platforms such as Twilio, Amazon Connect, Genesys, or LiveKit

  • Bonus points for experience building customer service, CRM, contact center, or workflow automation tools

  • Familiarity with travel industry technologies (PSS/GDS, hotel PMS/CRS) is a plus, though not required

Perks and benefits of working with us

  • Well-funded and proven startup with large ambitions, competitive salary, upsides of pre-IPO equity packages

  • Hopper covers the cost of employee premiums for private medical and dental coverage

  • Hopper also offers private life and accident coverage

  • Please ask us about our very generous parental leave, much above industry standards

  • Access to co-working space on demand through FlexDesk and a work-from-home stipend

  • Unlimited PTO

  • Hopper offers a monthly cash allowance for gym memberships and to cover home office expenses for a comfortable remote working experience

  • Carrot Cash travel stipend

  • Entrepreneurial culture where pushing limits and taking risks is everyday business

  • Open communication with management and company leadership

  • Small, dynamic teams, massive impact

About Hopper

At Hopper, we are on a mission to become the leading travel platform globally, powering Hopper's mobile app, website and our B2B business, HTS (Hopper Technology Solutions). By leveraging massive amounts of data and advanced machine learning algorithms, Hopper combines its world-class travel agency offering with proprietary fintech products to bring transparency, flexibility and savings to travelers globally. We have developed several unique fintech solutions that address everything from pricing volatility to trip disruptions, helping people travel better and save more on their trips.

The Hopper platform serves hundreds of millions of travelers globally and continues to capture market share around the world. The Hopper app has been downloaded over 120 million times and has become largely popular among younger travelers, with 70% of its users being Gen Z and millennials.

While everyone knows us as the Gen Z and Millennial travel app, Hopper has evolved to become much more than that. In recent years, we've grown into a travel fintech provider, commerce platform, and global travel agency that powers some of the world's largest brands.

Through HTS, our B2B division, the company supercharges its partners' direct channels by integrating our fintech products on their sites or powering end-to-end travel portals. Today, our partners include leading travel brands like Capital One, Nubank, Air Canada, and many more.

Here are just a few stats that demonstrate the company's recent growth:

  • Billions of dollars worth of travel and travel fintech are sold through Hopper and HTS' channels every year.

  • Our fintech products, including Cancel for Any Reason and Flight Disruption Assistance, have exceptionally strong CSAT because the terms are always clear, and customers receive instant, no-questions-asked resolutions.

  • Almost 30% of our app customers purchase at least one fintech product when making a booking, and consumers are 1.6x more likely to repurchase if they add fintech to their booking versus if they booked just travel.

  • Given the success of its fintech products, Hopper launched a B2B initiative, HTS (Hopper Technology Solutions), which represents more than 75% of the business.

Through HTS, any travel provider (airlines, hotels, banks, travel agencies, etc.) can integrate and seamlessly distribute Hopper's fintech or travel inventory on their direct channels. As its first HTS partnership, the company partnered with Capital One to co-develop Capital One Travel, a new travel portal designed specifically for cardholders. Other HTS partners include Air Canada, Uber, CommBank, Nubank, Flair Airlines and many more.

Hopper has been named the #1 most innovative company in travel by Fast Company. Hopper has been downloaded over 120 million times and continues to have millions of new installs each month. Hopper is now the #3 largest online travel agency in North America and 70% of our app customers are Gen Z and millennial travelers.

Hopper has raised over $750 million USD of private capital and is backed by some of the largest institutional investors and banks in the world. HTS is primed to continue its growth as the leading travel ecommerce provider in a $1 trillion online shopping category. The Hopper app and website will also continue to be the preferred travel provider for Gen Z and Millennials.

Come take off with us!

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