Software Engineer - Platform Infrastructure

ABOUT AFTERQUERY AfterQuery https://www.afterquery.com/ is an applied research lab curating data solutions for foundation model development. We serve every frontier AI lab with the mission of delivering the best data to power the best models. In doing so, we can make expertise that once took a lifetime to build available to anyone who needs it. Our customers are the ones building the foundation models themselves and our work sits directly in the loop of how those systems improve. This is a rare opportunity to join a company at a defining moment in AI. Forbes reported that we could be YC's fastest unicorn, reportedly raising at a $3.2 billion valuation. We're based in San Francisco and backed by leading investors including Altos Ventures, BoxGroup, and Y Combinator and angels from Google DeepMind, OpenAI, Anthropic, Meta Superintelligence Labs, and Microsoft AI. WHY APPLY Massive Opportunity: Forbes reported that we could be YC's fastest unicorn, reportedly raising at a $3.2 billion valuation, and we're not slowing down. Founding Impact: You will own and architect core infrastructure systems that power our platform from the ground up. Equity & Growth: Competitive salary and meaningful equity. As we scale, you’ll have the opportunity to shape the engineering organization and lead major technical initiatives. Strong Team: Our founding team has experience from Citadel Securities, Meta, Google, Silver Lake, and Morgan Stanley — work alongside world-class engineers and researchers. OVERVIEW As a Software Engineer - Platform Infrastructure at AfterQuery, you will design and build the core infrastructure that powers our data generation, evaluation, and agentic systems. You will be responsible for the shared platforms that enable our engineers and research teams to run large-scale human-in-the-loop workflows, evaluation harnesses, and automated data pipelines used to train frontier AI models. This is a highly technical role with broad ownership. You will architect and build foundational infrastructure that many other engineers depend on, ensuring systems are scalable, reliable, and capable of supporting extremely high-throughput workloads. You will work directly with the founding team to define system architecture, establish engineering best practices, and build the infrastructure that supports the next generation of AI development. RESPONSIBILITIES - Architect and develop the shared infrastructure powering our data generation platforms, human-in-the-loop systems, and evaluation pipelines. - Build systems capable of processing large-scale datasets and high-throughput workloads with strong reliability guarantees. - Create reusable infrastructure and APIs that enable product engineers and researchers to build quickly and reliably on top of core systems. - Design systems with strong observability, monitoring, and fault tolerance to support production workloads at scale. - Help define long-term system architecture across data pipelines, compute infrastructure, task orchestration, and storage systems. - Work closely with engineers and researchers to support new AI experimentation workflows and platform capabilities. - Define standards for system design, deployment, reliability, and infrastructure operations. REQUIRED QUALIFICATIONS - Strong experience building production distributed systems or platform infrastructure - Proficiency in Python and/or JavaScript (Node.js / Next.js) or similar backend technologies - Experience designing and operating systems in cloud environments (GCP or AWS) - Experience with message queues and event-driven systems (Kafka, RabbitMQ, Pub/Sub, etc.) - Experience working with high-throughput data pipelines and asynchronous processing systems - Strong understanding of system scalability, performance, and reliability - Experience owning systems running in production environments PREFERRED QUALIFICATIONS - Experience building internal developer platforms or shared infrastructure - Experience supporting large-scale data processing pipelines - Experience with AI infrastructure, LLM evaluation systems, or ML pipelines - Experience working at high-growth startups or scaling early infrastructure - Experience designing human-in-the-loop or workflow orchestration systems COMPANY BENEFITS (FOR ELIGIBLE EMPLOYEES): - Health Insurance: Medical, Vision, Dental - 401(k) with Employer Match - Daily Meals: Daily UberEats Stipend - Monthly Wellness Stipend We are an equal opportunity employer committed to providing a workplace free from discrimination and harassment. Employment decisions are made without regard to legally protected characteristics under applicable federal, state, or local law. We comply with applicable pay transparency requirements and provide compensation ranges based on the position, qualifications, experience, and other relevant factors. Reasonable accommodations are available to qualified individuals with disabilities and for sincerely held religious beliefs, as required by law. This job description is intended to describe the general nature and level of work performed and is not an exhaustive list of all duties, responsibilities, qualifications, or working conditions associated with the position. We reserve the right to modify this job description as business needs change.