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

Expected, Ruby on Rails, React.js

About 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., , Tech stack, React + TypeScript on the frontend, Ruby on Rails on the backend, some Node/TypeScript services, PostgreSQL underneath.

Your responsibilities, 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.

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.

Optional, 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

Benefits, private medical care, remote work opportunities, flexible working time, integration events, corporate library, no dress code, coffee / tea, employee referral program, charity initiatives, extra leave

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.

Monterail Sp. z o.o., We are Monterail - a team of ~ 130 experts working together to create meaningful software.As a software agency, we collaborate with multiple clients, so as a Junior Project Manager, you will most likely run a few projects simultaneously. We specialise in 4 main industries Fintech, MedTech, HRtech & E-commerce., , Our Delivery team is 7 PMs and 3 Delivery Managers — and we're growing.

This is how we work,