Senior Software Engineer – Infrastructure/Platform — AfterQuery

Location: San Francisco, CA (Onsite)
Compensation: $180,000 - $220,000
Visa Sponsorship: None available
Experience Level: Senior (5+ years)
Employment Type: Full-Time

AfterQuery is a high-growth AI research company building training data and evaluation infrastructure for frontier model labs. 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 a DevOps support role. This is not pure backend CRUD engineering. This is deep architecture ownership at founding-team velocity.

Core ownership includes:

• Shared infrastructure powering data generation, evaluation systems, and agentic workflows
• Scalable distributed systems supporting high-throughput asynchronous workloads
• Reusable APIs and internal infrastructure platforms for engineering and research teams
• Observability, monitoring, resilience, fault tolerance, and production reliability
• Long-term platform architecture across compute, orchestration, storage, and data systems
• Engineering standards for deployment, reliability, and platform operations

• Build and architect shared infrastructure powering data generation, evaluation systems, and agentic workflows
• Design scalable distributed systems supporting high-throughput asynchronous workloads
• Create reusable APIs and internal infrastructure platforms for engineering and research teams
• Own observability, monitoring, resilience, fault tolerance, and production reliability
• Define long-term platform architecture across compute, orchestration, storage, and data systems
• Partner directly with founders and technical leadership on infrastructure strategy
• Establish engineering standards for deployment, reliability, and platform operations

• 5+ years building and owning production distributed systems or platform infrastructure
• Strong backend engineering in Python and/or JavaScript (Node.js / Next.js)
• AWS or GCP cloud infrastructure experience
• Message queue and event-driven architecture experience (Kafka, RabbitMQ, Pub/Sub, or equivalent)
• High-throughput async data pipeline experience
• Strong systems scalability, performance, and reliability depth
• End-to-end ownership of production systems at scale
• Strong startup or FAANG-caliber engineering background highly preferred

Strong signals include backgrounds from FAANG, Jane Street, Citadel, Stripe, Ramp, and top-tier YC startups — particularly those with internal developer platform ownership, shared infrastructure leadership, AI infra or LLM eval infrastructure experience, and early-stage infrastructure scaling experience.

• Mid-level ICs without architecture ownership
• Legacy enterprise-only backgrounds
• DevOps-only profiles without strong software engineering ownership
• Infrastructure support engineers — this role is for true builders
• Candidates without end-to-end production ownership

1. Initial screen
2. Second round
3. Internal system design
4. External system design
5. 1-day work trial
6. References
7. 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.