Senior Software Engineer - Infrastructure
Afterquery · San Francisco
About this role
## Senior Software Engineer - Infrastructure ### About AfterQuery AfterQuery (https://www.afterquery.com/) is an applied research lab curating data solutions for foundation model development. We serve frontier AI labs with the mission of delivering the best data to power the best models—making expertise that once took a lifetime available to anyone who needs it. We work directly in the loop of how foundation models improve. This is a rare opportunity to join a company at a defining moment in AI. AfterQuery is YC’s fastest unicorn, valued at $3.2B, based in San Francisco, and backed by leading investors including Altos Ventures, BoxGroup, and Y Combinator, with angels from Google DeepMind, OpenAI, Anthropic, Meta Superintelligence Labs, and Microsoft AI. ### Why Apply - **Massive Opportunity:** YC’s fastest unicorn valued at $3.2B - **Founding Impact:** Own and architect core infrastructure systems powering the platform - **Equity & Growth:** Competitive salary and meaningful equity; help shape the engineering org - **Strong Team:** Founding team with experience from Citadel Securities, Meta, Google, Silver Lake, and Morgan Stanley ### Overview As a **Senior Software Engineer - Infrastructure**, you will design and build the core infrastructure powering AfterQuery’s **data generation, evaluation, and agentic systems**. You’ll be responsible for shared platforms enabling large-scale **human-in-the-loop workflows**, **evaluation harnesses**, and **automated data pipelines** used to train frontier AI models. This role has broad ownership: you’ll architect foundational infrastructure that many engineers depend on, ensuring systems are **scalable, reliable, and capable of extremely high-throughput workloads**. You’ll work closely with the founding team to define system architecture, establish engineering best practices, and build infrastructure supporting the next generation of AI development. ### Responsibilities - Architect and develop shared infrastructure powering data generation platforms, human-in-the-loop systems, and evaluation pipelines - Build systems for processing large-scale datasets and high-throughput workloads with strong reliability guarantees - Create reusable infrastructure and APIs so product engineers and researchers can build quickly and reliably - Design systems with strong observability, monitoring, and fault tolerance for production at scale - Help define long-term system architecture across data pipelines, compute infrastructure, task orchestration, and storage - Partner 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** - Strong understanding of **scalability, performance, and reliability** - Experience owning systems running in **production** ### Preferred Qualifications - Experience building internal developer platforms or shared infrastructure - Experience supporting large-sca
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