Senior Backend Engineer (LLM / AI Experience)

We're looking for a Senior Backend Engineer with recent LLM product experience who combines strong architectural thinking with hands-on development.

You'll work closely with the Head of Engineering, playing a key role in technical decisions while remaining deeply involved in day-to-day coding, feature delivery, and system optimization. You'll be a senior technical voice on the team - someone who designs systems and builds them., * Actively participate in architectural decisions with the Head of Engineering

• Collaborate with the Cloud Infrastructure Engineer on platform architecture, observability (monitoring, logging, alerting), and deployment strategies
• Design and optimize systems: performance profiling, database queries, caching, and resource usage
• Own production operations: troubleshooting, incident response, and on-call
• Provide technical guidance through code reviews, design discussions, and best practices
• Collaborate on real-time streaming architecture with the Video Synthesis Engineer

Feature Development & Implementation (50%)

• Implement backend features and services in production-grade Python and Go
• Build conversation features: state management, history, and intelligence improvements
• Implement multi-document knowledge bases using AWS Bedrock
• Integrate LLM APIs (OpenAI, AWS Bedrock) and build RAG pipelines
• Develop APIs and service integrations (gRPC, REST)
• Work on core backend services: orchestration, caching, and platform APIs
• Own testing, CI/CD pipelines, and deployment automation

Tech Stack

• Python (FastAPI) and Go (gRPC services)
• AWS (S3, EC2, Lambda, Bedrock, managed services)
• Docker, Kubernetes, RabbitMQ, Redis
• LLM APIs (OpenAI, AWS Bedrock), * Core backend services and RAG pipeline running reliably in production
• Platform-wide performance optimizations delivered (Q1-Q3 targets met)
• Backend engineers unblocked and supported through your technical guidance
• Recognized as the go-to expert for backend + LLM implementation, * Ownership of critical backend services used daily by enterprise customers
• Hands-on technical work alongside architectural responsibility
• Deep technical challenges across LLMs, RAG pipelines, real-time systems, and scalability
• High-impact role in a small, senior team (12 people)
• Close collaboration with Engineering, AI research, and infrastructure teams
• Opportunity to build expertise in the fast-evolving digital humans domain

Do you have experience in gRPC?, Do you have a Master's degree?, * 5+ years of backend engineering experience with distributed systems, microservices, and real-time architectures (WebSocket, gRPC, event-driven)

• Experience building and deploying complex, highly-performant Python applications

• 2+ years building LLM-powered products in production (2022-2025), including hands-on experience with LLM APIs (OpenAI, Anthropic, AWS Bedrock) and RAG systems

• Comfortable balancing architecture design with hands-on implementation

• Strong AWS experience with focus on performance optimization, observability, and production operations

• Proven ability to optimize production systems (latency, throughput, technical debt)

• Excellent collaboration skills across backend, infrastructure, and AI/ML teams, * Golang experience

• Experience with video streaming, media processing, or conversational AI platforms

• Data engineering or ML model serving infrastructure experience, * Knowledge transfer completed and ownership of critical backend services established

• Multi-document knowledge base and conversation features live in production

• Active contributor to architecture discussions with measurable performance improvements

• Production systems well-monitored with improved observability, * A short motivation (3-5 sentences) covering:

• Backend systems you've built and maintained

• LLM features you've implemented in production

• A performance optimization project you worked on

• Your experience with RAG or knowledge bases

• Why digital humans excite you, 2. Technical interview with Head of Engineering & Product Manager (90 min)

3. Team meeting with backend video synthesis, and/or infrastructure engineers (90 min)

4. Practical exercise (short, relevant implementation task)

• Build and scale backend systems powering conversational AI & digital humans
• Hands-on senior role balancing architecture + production code
• Work deeply with LLMs, RAG pipelines, and real-time systems Barcelona (hybrid) or remote in Europe |
• €50k-€65k

Why this role is exciting: You'll shape the backend foundations of a cutting-edge digital human platform, where your architectural and performance decisions directly impact real-time AI experiences used by enterprise customers.

At UNITH, we're transforming customer journeys with conversational AI. Listed on the ASX, we create lifelike digital humans using cutting-edge synthetic facial movement, voice engineering, and conversational design. Our digital humans speak 60+ languages with 600+ voices, redefining how businesses interact with customers worldwide.