Cello is the Revenue Growth Infrastructure for modern digital businesses. We help teams acquire, retain, and monetize customers at scale by turning word-of-mouth into a systematic, measurable growth channel - built for the AI era.

We’ve raised $10.3M total funding led by top-tier investors, and we’re now looking for a Senior Software Engineer - Full Stack (m/f/x) to help us realize our committed vision.

TL;DR

• Seed, GrowthTech
• Remote-first, Europe-based (must be within CET +/-3 hours)
• Competitive salary + eVSOPS

Why join

• GrowthTech scale-up with $10.3M in funding from top-tier investors.
• Exciting product: APIs, attribution models, MCP integration, AI-based recommendation engines, and assistants - not your typical CRUD app.
• Real traction - 30+ new customers every month, 10M+ end users monthly.
• Small team, so you'll genuinely shape how we build things.
• You'll touch everything from frontend widgets to backend infrastructure to data pipelines. The work doesn't get repetitive.
• We actively learn about new tech and AI tools and adopt where we can — we have to, because our customers do.
• Remote-first, but we get together regularly - company-wide and as an engineering team.
• The founding team consists of serial founders and experienced big-tech operators from Twilio, Wise, and Skype.

What We’re Building

We help SaaS companies turn their users and partners into a sales channel through referrals, sharing, and recommendations - 10M+ end users interact with our system every month.

Our widgets live inside customer products, which means your code runs in environments you don't control. On top of that: APIs that customer developers integrate against, and a portal where customers manage their campaigns and analytics.

Under the hood: attribution across complex user journeys, AI-based recommendation engines, multi-tenant infrastructure serving hundreds of customers, scaling millions of events. Deeper than you'd expect from a referral tool.
Our product is integrated by customer developers - and that world is changing fast. The people building against our APIs and widgets range from corporate engineering teams to solo founders using AI coding agents. Keeping up with how developers work today, and making sure our product fits into all of those workflows, is one of the more interesting challenges here.

Job Description

• Stack: React · NestJS · Python
• You'll start with well-scoped tasks and ramp up from there - we don't expect you to know everything on day one.
• Build features, fix bugs, and gradually take on more ownership as you learn the product.
• You'll work alongside senior engineers who'll help you grow, but we won't spoon-feed you either.
• We use AI tools heavily in our workflow - you'll be expected to leverage them to move fast and learn faster.

Required

• Good English (written & spoken)
• Some experience with React (or similar) and NestJS/Python (or similar) - you don't need years, but you need to have built something real.
• Hungry to learn. What you might lack in experience, you make up in energy and curiosity.
• You're enthusiastic about AI tools and actively use them to punch above your weight - but you've also written code that works without AI doing the thinking for you.
• Eager to learn the product and the domain, not just the tech.
• Strong work ethic - you take ownership, ship what you commit to, and don't need to be chased

Nice-to-haves

• Experience with mobile development (React Native, Flutter, etc.)
• AWS exposure - not a must, but willingness to learn is
• Side projects or a portfolio that shows you like building things

In the end, it’s all about the team and our culture. Understand why we love our job and see what it’s like to work at Cello in our People Playbook. We have some compelling perks and benefits: