Senior Software Engineer - Security/Infrastructure
Afterquery · San Francisco
About this role
## Senior Software Engineer — Security/Infrastructure ### About AfterQuery AfterQuery 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—helping make expertise that once took a lifetime available to anyone who needs it. We’re 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:** Join a fast-moving company (YC’s fastest unicorn) valued at **$3.2B**. - **Founding impact:** Own and architect core infrastructure systems from the ground up. - **Equity & growth:** Competitive salary and meaningful equity; shape the engineering org as we scale. - **Strong team:** Founding team experience from Citadel Securities, Meta, Google, Silver Lake, Morgan Stanley, and more. ### Overview As **Senior SWE — Security/Infrastructure**, you’ll protect systems that handle highly sensitive workflows across **AI training**, **expert networks**, and **enterprise integrations** with leading model labs. This is a deeply technical role: you’ll design and implement infrastructure that keeps systems resilient—not just manage off-the-shelf security tools. You should be comfortable using **LLMs** to accelerate debugging, threat analysis, and system design, and replacing repetitive work with code. When you’re not focused on security, you’ll build core systems such as **human-in-the-loop platforms** and **data infrastructure** that power frontier AI model development. **Work style:** In-person in **San Francisco**. ### Responsibilities - Build systems to **identify and respond to real security events** across the stack - Replace manual security workflows with **programmatic, scalable solutions** - Strengthen **cloud and production environments** (GCP/AWS, containers, networking) - Design and enforce **access control** across internal teams, experts, and customers - Integrate security checks into development workflows **without slowing shipping** - Own **incident handling** from detection through resolution - Secure AI-specific surfaces, including **data flows** and **model interaction layers** - Develop **human-in-the-loop** systems for AI training and evaluation - Contribute to core infrastructure and internal tooling across the company - Ship features across the stack that directly impact customers and model performance ### Required Qualifications - Built internal tools/systems to solve security problems (not just configured existing products) - Strong programming ability in **Python, Go, or TypeScript** - Experience with cloud environments (**IAM, networking, containers**) - Ability to identify vulnerabilities in **code and system design** - Experience creating/maintaining **signal-based monitoring and alerting** - Comfortable owning production issues - Able to move fluidly between security work and general engineering - **2–7 years** building software or security systems ### Preferred Qualifications - Background in fast-scaling startups or high-output engineering teams - Exposure to AI systems, data pipelines, or model evaluation workflows - Familiarity with offensive security techniques - Experience building tools other engineers depend on - Evidence of shipping systems from **zero to production** ### Company Benefits (for eligible empl
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