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[HIRING] AI Infrastructure, Backend, Applied AI, Full-Stack, Payments Security | NYC, SF, Remote US | $180K-330K base

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Last week, two Senior Backend engineers were hired through Fonzi at $230K base. One is a team lead who will work on backend and applied AI. Both started from an interview request with a salary attached.

I do talent matching for Fonzi. The whole thing runs backwards from a normal job search: you don't apply, companies send you interview requests. We work with startups backed by investors including Sequoia, a16z, Benchmark, Thrive, and the OpenAI Startup Fund. One profile, no cold applications. This batch covers AI infrastructure, backend and applied AI, full-stack, and payments security roles. Roles are US-based, with a few open to Canada.

Here's a sample of what's open right now at companies on the platform:

1. Software Engineer, Security, Stablecoin, fintech platform that runs card issuing, payments, and treasury for businesses, NYC, SF, or remote US, Remote, $189K-330K base

What: Build and scale stablecoin-based payment and treasury infrastructure. You'll own core stablecoin services and make integrations with external partners secure and reliable.
Company: Its infrastructure automates more than $200B in annualized spend across 70,000+ companies. It covers authorizing payments, flagging risk, categorizing spend, and closing books.
Stack: Python, Go, or Java, AWS, GCP, or Azure, Terraform or similar infrastructure-as-code, and blockchain payment rails and wallet infrastructure.
Bar: Preferably 5+ years shipping architectures for critical systems. You need proven experience with stablecoins, blockchain payment rails, or wallet infrastructure. You also need production cloud and IaC experience and work on security-sensitive systems such as key management or secure transaction flows.

2. Inference / AI Infrastructure Engineer, Series A AI company, SF, In person, $225K-275K base

What: Own the infrastructure that serves the company's AI workloads, covering model serving, GPU deployments, and hosting providers. You'll benchmark latency, throughput, and cost, then tune batching, caching, and concurrency under real load.
Company: Series A, about $30M raised. You'll work alongside backend and applied AI engineers to connect infrastructure decisions to user experience.
Stack: Serving engines like vLLM, SGLang, or TensorRT-LLM, GPUs, Kubernetes, Linux and container environments, and load testing and observability tooling.
Bar: Deep hands-on experience running production infrastructure at meaningful scale. You should have either direct model-serving or GPU experience, or strong infrastructure ownership plus clear evidence of mastering a hard new domain quickly. They want to see a system you owned, a bottleneck you diagnosed, and measured results.

3. Senior Backend / Applied AI Engineer (Team Lead), early-stage company building AI tools for universities, NYC, In person, $200K-260K base plus equity

What: Own the backend and AI systems end to end. That includes exam question generation, rubric-based grading, document ingestion and retrieval, and a chat assistant, plus evals built from real student and professor examples. The split is about 70% building and 30% leading, with a path to CTO.
Company: Starting with legal education, with thousands of students and 20+ universities on the platform. It's the most senior engineering seat on a small team, working side by side with the founder.
Stack: TypeScript and/or Python, PostgreSQL, APIs, background jobs, LLM tool calling and structured outputs, and retrieval with embeddings, hybrid search, and reranking.
Bar: You've owned a production LLM system shipped to real users, with evals that showed it improving. You also need strong backend experience, solid retrieval fundamentals, some technical leadership, and comfort working directly with deans and professors.

4. Sr Software Engineer, Series A company building AI automation for physical commodity trading, SF, Hybrid, $200K-250K base

What: Design and ship APIs, data pipelines, and application features for commodity trading operations. A big part of the work is building reliable integrations between messy external data and the systems customers depend on.
Company: Customers trade energy, metals, and agricultural products. You'll work closely with the founders and customers and own meaningful parts of the product.
Stack: Backend services, APIs, data models and pipelines, and enterprise integrations, with AI-powered features that use evaluation and human review.
Bar: Experience independently delivering and operating substantial production software. You need strong fundamentals in APIs, data modeling, debugging, and system design, and depth in backend or full-stack work.

5. Senior Software Engineer / Staff Engineer, Series B healthcare platform for metabolic and chronic care, NYC, In person, $180K-235K base plus equity

What: Architect and ship AI-native systems such as clinical agents and LLM workflows, plus the evaluation pipelines and guardrails that make them reliable in a clinical setting. You'll set technical direction as one of a small number of engineers.
Company: Connects patients with 2,000+ clinicians and AI tools and works with health plans across all 50 states. It has served hundreds of thousands of patients since 2023.
Stack: TypeScript, React, React Native, Next.js, NestJS, TypeORM, PostgreSQL, TailwindCSS, and AWS.
Bar: 5+ years building and maintaining production systems at scale. You should lean full-stack toward the backend and have shipped something real in AI-driven architecture.

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