Senior .NET Backend Engineer

Workana

3d•Remote

About The Position

SalesBlue is a voice AI sales automation platform for insurance brokerages in Mexico and Spain. We build outbound calling systems, campaign orchestrators, and agentic workflows integrating telephony, LLMs, carrier portals, and CRMs. This is a complex backend role in a real client, fast-paced environment. We are looking for a senior .NET/C# engineer who has operated real production systems under load, not just built them. The ideal candidate thinks in architecture first, can design for resilience and scale, and understands the importance of keeping a highly integrated backend alive across many moving parts.

Requirements

Deep .NET / C# expertise.
Strong CS fundamentals: OOP, SOLID, SOA, design patterns.
Experience designing and operating event-driven backend architectures.
Experience running systems on multi-server infrastructure with real traffic, understanding horizontal scaling, failover, and stateless design.
Proficiency with parallel and concurrent programming (async/await, thread safety, queues).
Experience integrating multiple external services/APIs within a single backend.
Ability to design backend architecture from scratch for complex web applications.
Fluent in AI dev tools: Claude Code, Cursor, GitHub Copilot.
Clear communication in English.

Nice To Haves

Voice AI / telephony integrations (Twilio, Retell, ElevenLabs, Deepgram).
AWS, Vercel, or Railway deployments.
Startup experience and comfort with shifting requirements.
Spanish language proficiency.

Responsibilities

Develop and maintain core backend services, including campaign orchestrators and FSM-based workflow engines.
Integrate with external services such as telephony (Twilio), voice AI platforms, insurance carriers, and CRMs.
Make system design and architecture decisions in collaboration with the CTO.
Implement multi-server deployments, async processing pipelines, and event-driven flows.
Support frontend integration via Next.js.