Senior Backend Engineer

Payflows; Paris; Hybride; EUR 70 000 - 110 000; Plein temps

Avantages offerts par ce poste

Flexible remote setup

Equity

Résumé du poste

Payflows is building an agent-driven finance platform in Paris and beyond. You’ll help develop backend services in Python, focusing on reliable APIs, data models, and deterministic workflows used by AI agents.

You’ll collaborate with product and frontend teams, own parts of the system, and contribute to production stability while enjoying a flexible remote setup in a small, human-sized team.

Qualifications

• Experience building backend services with Python.
• Familiarity with APIs and data models.
• Comfort working in an early-stage product.

Responsabilités

• Design and implement new services for product features.
• Refactor existing services for robustness.
• Investigate performance or production issues.
• Collaborate with product and frontend to shape features.
• Review code and mentor teammates.
• Build backend tools used by AI agents.
• Design safe, deterministic workflows for agent actions.

Connaissances

Autonomy

Ownership

Curiosity

Communication

Outils

Python

FastAPI

Pydantic

PostgreSQL

AWS

Serverless

Rust

Description du poste

About Payflows

At Payflows, we build software that helps large companies manage and automate their payment workflows. It’s not the flashiest part of a business, but it’s one of the most critical: invoices, approvals, payments, and controls. When these things slow down, the whole company feels it.

But our ambition goes further than just building a better workflow tool.

We believe the future of finance operations is not faster clicking: it’s no clicking at all

Finance teams shouldn’t spend their days moving data from one screen to another. Software should do the operational work, and humans should focus on reviewing, approving, and making the decisions that matter.

That’s the direction we’re building toward: an agent-driven finance platform, where intelligent agents handle the repetitive tasks, and users stay in control.

We started in 2022 with a small team and a rough first version of the product. Three years later, we’re working with major companies across France, the UK, and the US while choosing to keep our team small and human-sized.

We moved fast, shipped a lot, and not everything was built in a perfect way. But it helped us learn quickly, sign real customers, and prove that the problem we’re solving truly matters.

In 2024, investors trusted us with a $25M Series A. That gives us the chance to keep growing while also strengthening our foundations and building the system that will power this agent-driven future.

Today, we’re about 35 people from many different countries, and we’re looking for a few amazing humans to join the next chapter.

What you’ll actually do

You’ll help build a product that real finance teams rely on every day.

For us, engineering is not just about clean code, it’s about reliability, clarity, and trust, especially when money and automation are involved.

In a typical week, you might:

• Design and implement new services for a product feature.
• Refactor an early service to make it more robust.
• Investigate a performance or production issue.
• Work with product and frontend to shape a new feature.
• Review code and help teammates improve.
• Build backend tools that our AI agents use to perform real finance operations.
• Design safe, deterministic workflows where agents propose actions and humans review them.

Your time will be split between building new features and improving what already exists. Both matter.

You won’t just build endpoints. You’ll help shape the execution layer that our agents rely on: the APIs, data models, and workflows that let them act safely in production.

You’ll work closely with product, frontend, and customer-facing teams. We expect engineers to take ownership of parts of the system and help make them more reliable over time.

Our current tech reality

Our stack evolves based on our challenges, but we care more about good design than trendy tools.

Python is our core language. It helps us move fast, keep the code readable, and fits naturally with our AI-driven approach. A growing part of the system is built around agents that use our backend as a set of reliable, deterministic tools.

• Core language: Python
• Backend: FastAPI + Pydantic
• Data: PostgreSQL
• Infra: AWS, serverless when it makes sense
• Performance: some Rust for critical paths
• Architecture: multi-service backend, simple enough to reason about

Some parts of the system are clean and well-tested. Others were built quickly and need love. That’s the phase we’re in.

Over the next year, we’ll focus on:

• Turning core workflows into reliable tools for our agents
• Simplifying services
• Improving tests and observability
• Making performance more predictable
• Cleaning up early code

We know we’re not perfect, but we care a lot about improving step by step.

Who's going to thrive with us

You’ll probably feel comfortable here if:

• You like building products people actually use.
• You are autonomous and take ownership of what you ship.
• You take initiative and lead by example.
• You’re curious and enjoy figuring things out.
• You’re pragmatic about trade-offs.
• You communicate with kindness and clarity.

This role is a great fit if you’re excited by the idea of:

• Building systems that are used by AI agents, not just humans.
• Designing reliable, safe automation in production.
• Working on a product that is still early and evolving quickly.

You don’t need to know everything about AI. But you should be curious about it and excited to work in a system where agents are part of the core product

What you’ll get from this role

• Real ownership over parts of the system.

• Direct impact on customers and product decisions.
• A small, human team where your work is visible and meaningful
• A mix of feature work, system design, and technical improvements.
• Exposure to real scaling and production challenges.
• The chance to help build an agent-driven product from the inside.

We offer:

• Competitive salary and equity.
• Flexible remote setup (we only ask you to be at the office the first 3 days of each month).
• A high-autonomy environment where you have real ownership and space to make an impact.
• Plenty of room to grow, take responsibility, and shape parts of the product.
• A culture based on trust, ownership, and clear communication.

This isn’t a huge corporate environment. In exchange, you get autonomy, responsibility, and the chance to shape a product that’s still early in its story—and help build what finance operations will look like in the next decade