Senior Software Engineer

Concentric Recruitment; Barcelona; Hybrid; EUR 90,000 - 130,000; Full time

Job summary

Concentric Recruitment partners with a client building next-generation AI-driven voice solutions. We seek a Senior/Principal Software Engineer to own features end-to-end on a TypeScript/Python stack in a hybrid Barcelona environment.

You will build scalable APIs for real-time voice interactions, integrate LLM workflows, STT/TTS, and work closely with founders and senior leaders to scale the platform.

Qualifications

• 5+ years of production experience with modern web stack.
• Experience with AI coding agents (Claude Code, Cursor, Codex).
• Ability to work autonomously and drive features end-to-end.
• Comfort with Docker, SQL, testing and scalable architecture.
• Fluent Spanish language required.

Responsibilities

• Building scalable APIs and services for real-time voice interactions.
• Developing product features end-to-end with React, TypeScript and AI infrastructure.
• Integrating LLM, STT and TTS workflows into production.
• Working on agentic and multi-agent workflows.
• Improving architecture, observability, testing and engineering quality.
• Working directly with the founders and senior team to shape the platform.

Skills

5+ years experience

AI coding agents

Docker

SQL

Testing

Spanish fluent

Tools

React

TypeScript

Python

LLM orchestration

OpenAI/Whisper

Job description

Role: Senior / Principal Software Engineer

Job Type: Full-Time

Contract Type: Direct employment with our client

Location: Hybrid - Barcelona

Language: Fluent Spanish is required

Visa sponsorship is not available for this role

[Only interested in speaking with candidates who are comfortable working in a hybrid model]

Our partner is building next-generation AI-driven communication products that help businesses automate customer interactions, improve operational efficiency and generate actionable insights in real time.

They are now looking for a Senior/ Principal Software Engineer to help scale the platform behind their voice agents, owning features end-to-end across their TypeScript / Python stack and working on AI pipelines, LLM orchestration, STT/TTS, prompt workflows and real-time systems.

What we are looking for

• +5 years of production experience with modern web stack
• Experience with AI coding agents such as Claude Code, Cursor or Codex
• Real Product mindset and ability to work autonomously
• Comfortable with Docker, SQL, testing and scalable architecture
• Fluent Spanish

Nice to have

• Experience with LLMs, STT/TTS, OpenAI, Whisper, ElevenLabs or Deepgram
• Experience with LangChain, LangGraph or similar AI orchestration tools
• AWS/GCP, CI/CD and observability experience
• Startup or early-stage product company experience
• Previous experince leading a team or acting as a principal

What you'll be doing

• Building scalable APIs and services for real-time voice interactions
• Developing product features end-to-end with React, TypeScript and AI infrastructure
• Integrating LLM, STT and TTS workflows into production
• Working on agentic and multi-agent workflows
• Improving architecture, observability, testing and engineering quality
• Working directly with the founders and senior team to shape the platform