Senior Software Engineer - Security/Infrastructure

AfterQuery Job OpportunityAfterQuery 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. Since raising our $30M Series A at a $300M valuation, AfterQuery has grown well over a $100M revenue run rate. 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.OverviewYou'll be responsible for protecting a system that handles highly sensitive workflows across AI training, expert networks, and enterprise integrations with leading model labs. This role is deeply technical. You'll design and implement the infrastructure that keeps our systems resilient, rather than managing off-the-shelf security tools. We move fast and rely heavily on AI internally. You should be comfortable using LLMs to accelerate debugging, threat analysis, and system design—and just as comfortable replacing repetitive work with code. Security here isn't isolated. When you're not working on security problems, you'll be building core systems—especially human-in-the-loop platforms and data infrastructure that power how frontier AI models are developed. We work in-person in San Francisco.ResponsibilitiesBuild systems that identify and respond to real security events across our stackReplace manual security workflows with programmatic, scalable solutionsStrengthen our cloud and production environments (GCP/AWS, containers, networking)Design and enforce access control systems across internal teams, experts, and customersIntegrate security checks directly into development workflows without slowing shipping speedOwn incident handling systems and processes from detection through resolutionSecure surfaces unique to AI systems, including data flows and model interaction layersDevelop human-in-the-loop systems used in AI training and evaluationContribute to core infrastructure and internal tooling used across the companyShip features across the stack that directly impact customers and model performanceRequired QualificationsYou've built internal tools or systems to solve security problems—not just configured existing productsStrong programming ability in Python, Go, or TypeScriptExperience working with cloud environments (IAM, networking, containers)Ability to identify vulnerabilities directly in code and system designExperience creating or maintaining signal-based monitoring and alerting systemsComfortable owning production issues when they ariseAble to move fluidly between security work and general engineering2-7 years building software or security systemsPreferred QualificationsBackground in fast-scaling startups or high-output engineering teamsExposure to AI systems, data pipelines, or model evaluation workflowsFamiliarity with offensive security techniquesExperience building tools that other engineers depend onEvidence of building and shipping systems from zero to production