Sr Software Engineer en Madrid, España

Sinch is pioneering the way the world communicates. More than 150,000 businesses - including Google, Uber, Paypal, Visa, Tinder, and many others - rely on Sinch’s Customer Communications Cloud to power engaging customer experiences through mobile messaging, voice, and email.

Whether you need to verify users or craft omnichannel campaigns, Sinch makes it easy. Our AI-infused Super Network, APIs, and applications ensure you can connect with your customers reliably and securely, at every step of their journey.

At Sinch we “Dream Big”, “Win Together”, “Keep it simple”, and “Make it Happen”. These values are our foundation!

Chatlayer Product is made up of two teams - Platform & Integration and Flow Engine & Intelligence Integration - sharing a single product roadmap and backlog under Engineering Manager JR Reynolds. Together the organization includes around 10 engineers, two tech leads, a product manager, and a UX designer. The teams value honesty, growth, knowledge sharing, collaboration, ownership, and “being pirates” - a bias toward bold, resourceful action. Communication happens primarily through Slack and Teams, and we have a strong culture of transparent decision-making and discoverable collaboration.

Chatlayer is building toward a future of conversations with control - where AI agents and deterministic workflows work in harmony to solve our customers’ problems. This means evolving from a traditional chatbot platform into an agentic orchestration system where intelligent automation is grounded by reliable, predictable flow execution. We’re looking for the right people to help us get there.

We are looking for a Senior Software Engineer to help design, build, and scale Chatlayer’s conversational AI platform. You will work across a real-time, distributed system that handles text and voice interactions at scale - including WebSocket infrastructure, bot engine integrations, and platform services. This role requires someone who is comfortable operating in ambiguity, can drive technical decisions, and thrives in a team that ships with urgency while investing in system health.

Candidates should bring a knowledgeable and skilled approach to the use of AI in the software development process itself - we value a balanced, curious, and quality-driven use of AI tooling. We’re not looking for engineers who blindly generate code or who refuse to adopt new tools; we want people who apply AI judiciously, maintaining deep comprehension of what they build while leveraging these tools to move faster and think bigger.

Key Responsibilities

• Design and build backend services supporting Chatlayer’s text and voice channels, including WebSocket servers and real-time communication infrastructure
• Work on platform integrations and app-integration frameworks
• Contribute to architectural evolution - decoupling legacy dependencies and building more modular, vendor-agnostic systems
• Participate in technical decisions around identity management (SinchID), distributed events and data processing (MongoDB Atlas, Kafka, Temporal), and new platform capabilities
• Lead code reviews, technical discussions, and knowledge-sharing sessions within the team
• Mentor and be mentored by other engineers and contribute to a strong engineering culture rooted in the team’s values
• Support production systems through on-call rotations and incident response
• Invest in system health - improving test coverage, addressing technical debt, and continuously improving operational processes (Kaizen)

Required Skills & Experience

• 5+ years of professional software engineering experience
• Strong proficiency in https://jobeax.com/link/XoOr05ZMdUyNwOHw and/or Go
• Experience with real-time systems - WebSocket, event-driven architectures, or similar
• Solid understanding and hands-on experience with complex cloud infrastructure, ideally GCP and/or AWS
• Experience with microservices architecture and distributed systems, including state management across replicas (e.g. ETCD, Redis)
• Working knowledge of MongoDB or similar document databases
• Experience building and maintaining RESTful APIs and event-driven architectures (ideally Kafka specifically)
• Strong system design fundamentals - can reason about scalability, latency, failover, and trade-offs
• Excellent communication skills and comfort working in a distributed, cross-functional team (CET timezone alignment preferred)

Preferred / Nice-to-Have

• Experience with conversational AI, chatbot or voicebot platforms, or NLP/NLU pipelines
• Experience with containerisation and orchestration (Docker, Kubernetes)
• Familiarity with identity management systems (OAuth/OIDC)
• Prior experience in a CPaaS, scale-up, or fast-growth product company

Our corporate language is English; please submit your application in English.

The salary for this position is for:

• Spain (Annual) : €60.000 - €80.000
• Sweden (monthly): 60.000 SEK - 75.000 SEK.
• Factors which may affect pay within this range may include skills, education, experience, and other qualifications

We are committed to ensuring a recruitment process that is fair, objective, consistent, and inclusive. Our approach includes structured, competency-based interviews designed to evaluate your skills, experience, and qualifications relevant to the role. At times, we may include a data-driven assessment to enhance our hiring success and identify candidates likely to excel.