Senior Backend Engineer

About AZXOur mission is to accelerate positive impact in critical industries through AI transformation. We specialize in physics-informed ML and enterprise AI solutions that directly address climate and sustainability challenges.We're growing quickly and already work with category-leaders in real estate (CBRE), energy (LevelTen Energy), logistics (Flexe) and utilities.We're a public benefit corporation, founded in 2024, and have been profitable from inception.We work on challenges in clean energy, decarbonization, climate risk, energy systems, and global economics. We're building our company for long-term success and aim to create the ultimate place to work for those passionate about AI and making a positive impact.About the RoleAs a Backend Engineer you will build the services our products and client solutions run on. The center of gravity is LLM infrastructure: the layer that puts one governed front door over many models, hosted and self-hosted, and answers the questions enterprises actually ask: who used which model, for what, at what cost, under whose rules. The platform's first customers are our own client-facing engineers, the people delivering client outcomes with what you build, so requirements arrive concrete, feedback arrives same-day, and the people you support are in the same meeting.ResponsibilitiesOwn the LLM gateway: routing, metering, budgets, guardrail composition, and provider/backend adapters across hosted and self-hosted models.Manage the retrieval and knowledge service: connectors, chunking, hybrid search and reranking, grounded answers, and the MCP surface.Build the eval harness that turns retrieval tuning from judgment into evidence, with confidence intervals and per-segment breakdowns.Own the async framework (its public API, rate-limit algorithms, and admin tooling) and lead its evolution into durable execution for agent runs.Design authorization across the whole surface: token hierarchies, capability grammars, and per-tenant isolation tested as a regression, not asserted in a doc.Own your own definition of done on everything you ship: evals, traces, cost accounting, and the dashboard that would wake you up.Additional InformationMust be willing to travel to Seattle area for final interview and travel 2x/year for company summitsApplicants must be currently authorized to work in the United States on a full-time basis.We are unable to sponsor or take over sponsorship of employment visas at this time.Please only apply to a maximum of 2 roles at a time; any applicants who apply to more than 2 roles within a 6 month period will automatically be disqualified.Next StepsIf this job sounds like a great fit but you don't check ALL of these qualification boxes, we'd still love to hear from you! Required Qualifications5+ years of deep, production async Python: cancellation scopes, streaming lifecycle, and connection pooling.Postgres as infrastructure: comfortable reasoning about MVCC, advisory locks, and vacuum discipline, with Redis/Dragonfly used (and not used) where it belongs; real distributed-systems experience, not just familiarity.Experience shipping API surfaces other engineers build on: versioning, idempotency, error vocabularies, migration discipline, and documentation to match.Depth in at least one of LLM gateway concerns (routing, metering, guardrails, provider failover) or retrieval engineering (hybrid search, reranking, eval methodology, audit-ready RAG), with credibility on the other.A cost accounting and evals first mindset: you've shipped a gate or harness that caught a real regression, ideally one of your own.Production depth in some modern stack, and the aptitude to ramp quickly on unfamiliar tools.Practical familiarity with our core stack: Python 3.12+ (async, type-strict, FastAPI/Starlette, Pydantic v2), asyncpg/SQLAlchemy, Postgres (incl. pgvector), and Redis/Dragonfly with Lua, with willingness to research into the rest.Exposure to the surrounding ecosystem: OpenTelemetry (incl. GenAI conventions), SSE/streaming lifecycles, OpenAI/Anthropic provider APIs, job frameworks (Celery/Dramatiq/Prefect-class), rate-limit algorithms (token bucket, GCRA), and integer-cents money handling.Past work in energy, real estate, utilities, climate or related fields is a plus.Experience in both startup and enterprise environments is a plus. Benefits & Perks Why AZX!Be part of a fast-growing, profitable, mission-driven company with industry-leading clients tackling the massive opportunity of AI transformation in critical industries.Competitive early-stage startup compensation (based on capabilities, experience, and location)Bonus eligibilityHealth insurance with meaningful coverage for dependentsFlexible paid time offEquityFully remote culture with a cluster of teammates in Seattle Equal Opportunity EmployerAZX is an equal opportunity employer. We are committed to building a diverse and inclusive team and do not discriminate on the basis of race, color, religion, sex, sexual orientation, gender identity or expression, national origin, age, disability, veteran status, or any other characteristic protected by applicable law.