Senior Fullstack Developer - Freelance (Ruby on Rails & React)

The project

Some products you use every day without ever seeing them. This is one of those.

Our client is a well-established B2D (business-to-developer) SaaS platform -real-time infrastructure that moves billions of messages a day for developers around the world. Live chat, dashboards, collaborative apps, state synchronization: if it updates in front of your eyes, there's a good chance technology like this is running underneath.

The role

This is a product-minded engineering role, not ticket execution. The team is deliberately moving away from reactive delivery toward engineers who understand customers and drive outcomes. You'll take features from a loose concept to shipped and monitored in production — dashboards, billing UIs, documentation platforms, developer-facing tools — proposing what should be built, not waiting for a roadmap to tell you.

And here's the fun part: the customers are developers. You'll use the product yourself and fix the frustrations you'd want fixed.

What we're looking for

• A fullstack craftsman. You're strong in Ruby on Rails and React and comfortable moving across the stack - from complex dashboards to sleek documentation platforms.
• A DevEx champion. You have natural empathy for other developers and genuinely care about the developer experience of the tools you build.
• Comfortable with ambiguity. You thrive when the brief is vague. You identify problems, propose solutions, and ship with minimal hand-holding.
• An owner. You see features through their entire lifecycle — from the first line of code to the final metric in production. Quality issues that surface after release are still yours.
• A proactive communicator. You give realistic estimates, meet your commitments, and speak up early if a timeline is at risk.
• Fluent with AI coding assistants. The team uses them actively for planning, prototyping, and iteration — you should too, while owning the correctness and quality of everything that ships.
• Design and UX intuition. You notice when a flow feels wrong and you're not afraid to say so.

• Tech stack
• React + TypeScript on the frontend, Ruby on Rails on the backend, some Node/TypeScript services, PostgreSQL underneath.
• Nice to have

• Experience building developer-first products or working on B2D platforms
• Experience with products grown through product-led growth (PLG)
• Background in real-time, messaging, or infrastructure-adjacent products

How the collaboration works

This is a freelance engagement through the Monterail Tech Network - you work with us on a B2B basis, embedded in the client's team, with Monterail handling the partnership side. Read more about what freelancing with us looks like at Monterail Tech Network .

Sound like you?

Send us your resume — and if you've built anything for developers before, we'd love to hear about it.