Senior Software Engineer, Go - LLM Team

Why AssemblyAI AssemblyAI builds the best-in-class Voice AI models powering the next generation of voice applications. Our models serve 600M+ inference calls monthly, process 1M+ hours of audio daily, and power 2 billion+ end-user experiences. The Voice AI space is at an inflection point; we’re looking for folks truly excited to join a small team and help define the future of the industry. We are one of the most capital-efficient AI companies on the planet - with under 100 people generating roughly $500K ARR per employee, we sit among the top 5 most revenue-dense teams within the fastest-growing AI companies today. That's not an accident; it's a deliberate choice to stay lean, move fast, and give every person on the team outsized ownership and impact. With thousands of customers including Granola, Fireflies, Figure AI, and CallRail, the company has real scale - processing over 2 million hours of audio daily and handling more than 1 million API calls every day. This is a rare growth-stage opportunity where the business is proven and the trajectory is steep, but the team is still small enough that your fingerprints are on everything. If you've ever felt buried under layers of bureaucracy, starved of real ownership, or frustrated watching your work disappear into a slow-moving org, AssemblyAI is built differently. The company operates as a true meritocracy, with no heavy planning or approval processes and no gatekeeping on the tools or information you need. For anyone who genuinely cares about voice AI, not as a trend to chase, but as a technology to build,  this is the place where the most interesting problems at the most interesting scale are being solved by a team small enough that you'll actually know everyone's name. We’re committed to creating a space where our employees can bring their full selves to work and have equal opportunity to succeed. No matter your race, gender identity or expression, sexual orientation, religion, origin, ability, age, veteran status, if joining this mission speaks to you, we encourage you to apply! About the Role We're seeking an exceptional Senior Software Engineer to join our LLM team. This role is focused on building and maintaining our LLM gateway service—a unified API platform that connects customers to multiple LLM providers. You'll work on high-impact projects that directly solve customer problems, improve their AI and agentic workflows, and ensure reliable access to the best models for their use cases. This is a deeply customer-focused role. You'll work closely with our customer success team to understand customer challenges, help optimize their prompt strategies, build features that address their pain points, and ensure our service reliably delivers value. We're looking for someone who combines software engineering excellence with genuine curiosity about how customers use AI and a drive to make their lives better. As a Senior Engineer, you'll drive technical execution within the team, taking ownership of significant features and integrations while mentoring more junior engineers. You should be passionate about writing clean, maintainable code, implementing comprehensive testing strategies, and building highly reliable systems in service of solving real customer problems. This role requires close collaboration with customer success, product managers, external API providers, and other engineering stakeholders. You'll need to balance technical excellence with pragmatic delivery in a fast-paced startup environment where uptime, reliability, and customer success are critical. What You'll Do Solve Customer Problems Partner closely with the customer success team to understand customer use cases, challenges, and integration needs Translate customer pain points surfaced by the CS team into technical solutions and product improvements Build features and tooling that directly address customer needs and improve their workflows Provide technical guidance and expertise to the customer success team to help them support customers effectively Drive Technical Execution Own and deliver complete features and integrations within our LLM gateway service Build and maintain integrations with multiple LLM providers and AI services (OpenAI, Anthropic, Google Vertex, AWS Bedrock etc.) Write clean, maintainable, well-tested code following best practices Design and implement scalable, fault-tolerant solutions with appropriate abstractions Proactively identify and address technical debt, reliability issues, and code quality concerns Participate in on-call rotation to ensure service reliability and rapid incident response Elevate Engineering Standards Conduct thorough code reviews focused on maintainability, testing, reliability, and architectural concerns Ensure proper test coverage across unit, integration, and end-to-end testing levels Improve code maintainability and extensibility through targeted refactoring Contribute to runbooks, incident po