AfterQuery — Senior Software Engineer, Infrastructure/Platform

Type: Full-time | On-site | San Francisco, CA Compensation: $250,000–$350,000 + competitive equity Hiring count: 2 Visa sponsorship: None available Reports to: TBD (screening interviewers named: Alec, Carlos)

AfterQuery is a research lab investigating the boundaries and capabilities of artificial intelligence through novel datasets and experimentation. Its customers are the frontier AI labs — every major foundation-model lab is a client. Backed by Y Combinator, BoxGroup, ex-partners from Lightspeed and Index Ventures, and senior leadership at Google DeepMind and Meta GenAI. One of the fastest-growing YC companies in its batch. Founding team drawn from Jane Street, Meta, Citadel Securities, Google, Goldman Sachs, Morgan Stanley, Silver Lake, Berkeley AI Research (BAIR), and Stanford AI Lab (SAIL).

Founded: 2025 | Team size: 11–50 | Stage: Series A Industry: AI research / data infrastructure (role page card mislabels this "Consumer Tech") Website: afterquery.com Office: San Francisco, CA

• Frontier-lab customer base: the infrastructure you build directly powers data generation and evaluation for every major foundation-model lab.
• Broad, foundational ownership: architect and own the core distributed systems the entire company depends on, working directly with the founding team to set architecture and standards.
• Caliber + upside: founding team from Jane Street, Citadel, Meta, Google, and Goldman; meaningful equity at an early, fast-scaling Series A YC company.

• Not provided on the role page. Request intake notes from Contrario if available.

Design and build the core infrastructure powering AfterQuery's data generation, evaluation, and agentic systems — the shared platforms that let engineers and researchers run large-scale human-in-the-loop workflows, evaluation harnesses, and automated data pipelines used to train frontier AI models. A highly technical role with broad ownership, working directly with the founding team.

• →Architect and develop the shared infrastructure powering data generation platforms, human-in-the-loop systems, and evaluation pipelines
• →Build systems capable of processing large-scale datasets and high-throughput workloads with strong reliability guarantees
• →Create reusable infrastructure and APIs that let product engineers and researchers build quickly and reliably on top of core systems
• →Design systems with strong observability, monitoring, and fault tolerance for production workloads at scale
• →Help define long-term system architecture across data pipelines, compute infrastructure, task orchestration, and storage systems
• →Work closely with engineers and researchers to support new AI experimentation workflows and platform capabilities
• →Define standards for system design, deployment, reliability, and infrastructure operations

Tech stack: Python and/or JavaScript (Node.js/Next.js); GCP or AWS; message queues / event-driven systems (Kafka, RabbitMQ, Pub/Sub)

• 5+ years building and owning production distributed systems or platform infrastructure
• Strong backend proficiency in Python and/or JavaScript (Node.js/Next.js)
• Cloud infrastructure experience in GCP or AWS
• Message queues and event-driven systems (Kafka, RabbitMQ, Pub/Sub)
• High-throughput data pipelines and asynchronous processing
• System scalability, performance, and reliability ownership
• Shared infrastructure, APIs, and internal platform development
• Observability, monitoring, and fault tolerance design
• Long-term architecture ownership across data pipelines, compute, and storage
• Cross-functional collaboration with engineering and research teams
• Undergraduate degree from the U.S., Canada, or the U.K

• Background at FAANG, Jane Street, Citadel, Stripe, Ramp, or top-tier YC company
• Has architected and owned production infrastructure end-to-end at scale
• Experience building internal developer platforms or shared infrastructure at senior level
• Experience with AI infrastructure, LLM evaluation systems, or ML pipelines
• Has scaled early infrastructure at a high-growth startup
• Experience designing human-in-the-loop or workflow orchestration systems
• Defined architecture decisions and set engineering standards, not just executed them

• Only mid-level or IC contributor experience with no architectural ownership
• Background exclusively at large legacy enterprises or slow-moving companies
• Has never owned a production system end-to-end
• No cloud infrastructure depth in GCP or AWS
• No experience with high-throughput or distributed systems
• Under 5 years of experience

Salary$250,000–$350,000EquityCompetitive / meaningful (Series A)On-site policyOn-site, San FranciscoVisa sponsorshipNone availableEmployment typeFull-timeLocationSan Francisco, CAHiring count2

• None provided on the role page.

Stage 1 — Initial Screen (Alec) — Recruiter/initial screen. Stage 2 — Second Round (Carlos) — Second-round interview. Stage 3 — System Design (Internal) — System-design interview with internal panel. Stage 4 — System Design (External) — System-design interview with external panel. Stage 5 — Work Trial (1 day) — One-day paid/working trial. Stage 6 — References — Reference checks. Stage 7 — Offer Extended Stage 8 — Candidate Hired — Candidate accepts and starts.

Updated [not dated on role page] No dedicated "Ideal Companies" section on the role page. Named target backgrounds appear in Green Flags: FAANG, Jane Street, Citadel, Stripe, Ramp, top-tier YC companies. Founding-team pedigree (as background signal): Jane Street, Meta, Citadel Securities, Google, Goldman Sachs, Morgan Stanley, Silver Lake, BAIR, SAIL.

For reference only — DO NOT CONTACT (per role page) / do not source these specific profiles.

• Xiaowei Jiang — LinkedIn URL not captured in page source
• Yawen D — LinkedIn URL not captured in page source
• Vedu Mallela — LinkedIn URL not captured in page source