Senior Software Engineer - Infrastructure/Platform AfterQuery

Senior Software Engineer – Infrastructure/Platform — AfterQuery Location: San Francisco, CA (Onsite) Compensation: $250,000 – $350,000 base + competitive equity Visa Sponsorship: None available Experience Level: Senior (5+ years) Employment Type: Full-Time About AfterQuery AfterQuery is a frontier AI research lab focused on pushing the boundaries of artificial intelligence through novel datasets, evaluation systems, experimentation, and agentic infrastructure. Every major frontier foundation model lab is reportedly a customer. AfterQuery is one of the fastest-growing Y Combinator companies from its batch, backed by Y Combinator, BoxGroup, former Lightspeed partners, and former Index Ventures partners, with leadership and advisor pedigree from Google DeepMind and Meta GenAI. Founding team backgrounds include Jane Street, Meta, Citadel Securities, Google, Goldman Sachs, Morgan Stanley, Silver Lake, Berkeley AI Research (BAIR), and Stanford AI Lab (SAIL). About the Role This is a senior infrastructure and platform engineering role supporting frontier AI data generation and evaluation systems. This is not DevOps support. This is not pure backend CRUD engineering. This is deep architecture ownership. Core ownership includes: Shared infrastructure powering data generation platforms Human-in-the-loop workflow systems Evaluation harness infrastructure Agentic systems platform engineering Large-scale asynchronous data processing pipelines Distributed compute architecture Task orchestration and storage architecture Internal platform APIs and shared engineering infrastructure Reliability, monitoring, observability, and fault tolerance engineering High-throughput distributed systems Long-term infrastructure architecture strategy What You'll Own Architect foundational infrastructure used across engineering teams Build distributed production systems at scale Design reusable platform components and shared APIs Support large-scale AI experimentation workflows Establish infrastructure engineering standards and deployment/reliability practices Enable rapid engineering velocity through platform architecture Requirements 5+ years of distributed systems and platform engineering experience Strong backend Python and/or JavaScript (Node.js / Next.js) AWS or GCP production infrastructure experience Message queue and event-driven architecture experience (Kafka, RabbitMQ, Pub/Sub, or equivalent) High-throughput async data pipeline experience Production scalability, performance optimization, and reliability engineering End-to-end production ownership with strong architectural ownership history Nice to Have Internal developer platform engineering Shared infrastructure ownership at scale AI infrastructure, LLM evaluation systems, or ML platform infrastructure Human-in-the-loop or workflow orchestration systems Startup scaling experience Target Backgrounds Strong signals include backgrounds from FAANG, Jane Street, Citadel, Stripe, Ramp, or top-tier YC startups with senior architecture ownership, shared platform engineering leadership, and high-scale infrastructure design. This Role Is NOT For Mid-level ICs without architecture ownership Legacy enterprise-only backgrounds Profiles without end-to-end production ownership Candidates with limited infrastructure scale exposure Benefits Competitive salary and meaningful equity Major technical ownership Opportunity to shape the engineering organization Work alongside frontier AI researchers and elite engineers Logistics Role is fully onsite in San Francisco — please only apply if you can commit to this No visa sponsorship available #J-18808-Ljbffr