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

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).

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

• 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

• 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

• 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

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.

• Mid-level ICs without architecture ownership
• Legacy enterprise-only backgrounds
• Profiles without end-to-end production ownership
• Candidates with limited infrastructure scale exposure

1. Pending approval
2. Initial screen (Alec)
3. Second round (Carlos)
4. System design — internal
5. System design — external
6. 1-day work trial
7. References
8. Offer

• Role is fully onsite in San Francisco — please only apply if you can commit to this
• No visa sponsorship available

Shortlisted candidates will be contacted by David Joseph & Co., the recruiting partner managing this search on behalf of AfterQuery.