Senior Software Engineer — AI Accounts Receivable · Fazeshift

Aionia Group; San Francisco (CA); On-site; USD 120,000 - 160,000; Full time

Job summary

Aionia Group in San Francisco is searching for a Senior Software Engineer to shape the architecture of their fintech platform. You'll have significant ownership of technical solutions and will collaborate closely with the founders to define product direction.

The ideal candidate should have 5+ years of full-stack engineering experience and have worked in either big tech or early-stage startups. This role demands full autonomy, and you'll be mentoring engineers through best practices.

Qualifications

• 5+ years of experience in full-stack software engineering.
• Experience in leading teams and mentoring engineers.
• Strong skills in products scaling and architecture.

Responsibilities

• Design and build full-stack features across the Next.js frontend and backend API layer.
• Lead schema design, migrations, and safety rollouts in a high-stakes fintech environment.
• Mentor engineers through code reviews and architectural guidance.

Skills

Full-stack software engineering

TypeScript proficiency

Node.js experience

Next.js knowledge

React skills

Education

Degree from a top-20 CS program

Tools

Prisma

Event-driven tools

Job description

Engineering · First Senior Hire · Fintech AI

Senior Software Engineer Shape the architecture. Set the bar.

About Fazeshift: Fazeshift is an AI-driven accounts receivable platform designed to help enterprises automate invoicing, cash application, and collections — improving efficiency, reducing errors, and accelerating revenue cycles. The platform automates invoice creation and distribution, enhances collections with AI‑powered reminders and predictive payment insights, and seamlessly integrates with ERP and accounting systems.

High-Stakes Domain: Correctness & Uptime Matter

This is fintech / AR automation. The work is consequential — enterprise clients rely on Fazeshift for accurate invoicing and cash flow. You'll be building systems where correctness is non‑negotiable and reliability is the standard.

Why This Role

You'll shape the architecture, set the engineering bar, and define what great looks like as the team scales. This is not an IC role in a large org. You'll collaborate directly with the founders on product direction and technical trade-offs from day one — not filtered through layers of management.

Real Ownership, Real Autonomy

Significant ownership over what gets built and how. Schema design, migrations, system design reviews, runbooks — the full technical scope is yours.

The Opportunity

We are looking for a Senior Software Engineer with 5+ years of experience to be the first senior engineering hire at Fazeshift — shaping architecture, shipping end‑to‑end features, and setting the bar for engineering quality as the team scales. You'll have significant ownership over what gets built and how, collaborating directly with founders on product direction and technical trade‑offs. If you thrive with autonomy and want to build the technical foundation of a fast‑growing fintech product, this is your role.

What You'll Do

• Design and build full‑stack features across the Next.js frontend and backend API layer
• Lead end‑to‑end schema design, migrations, and backfills across Prisma and MySQL — designing rollouts that are safe to deploy in a high‑stakes fintech environment
• Set the bar for engineering practices through system design reviews, incident response, runbooks, and observability
• Mentor other engineers through code review and architectural guidance — you are raising the floor for the whole team
• Collaborate directly with founders on product direction and technical trade‑offs that will define the platform for years

Requirements

Required

• 5+ years of experience in full‑stack software engineering
• Experience in big tech — FAANG or faster (e.g. Databricks, Square) — or VC‑backed startups, early‑stage preferred
• Experience at an early‑stage startup (sub‑30 people)
• Scaled a B2B SaaS product from early users to meaningful ARR
• Strong full‑stack development skills including proficiency in TypeScript
• Proficient with Node.js, Next.js, React, Vercel, or Prisma

Nice to Have

• Proficient with event‑driven tools like Inngest or Temporal
• Track record mentoring engineers via code review and design reviews
• Degree from a top‑20 CS program

Traits to Avoid

• Needs direction or defined scope to be productive — this role demands self‑driven ownership
• Only worked on large teams with narrow ownership — this is not a ticket‑taker role
• Prefers backend‑only or frontend‑only work — full‑stack ownership is required