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

Monterail; Wrocław, Warszawa; On-site; PLN 89,280 - 133,920; Part time

Job summary

Monterail is seeking a freelance fullstack engineer to collaborate remotely on a B2B SaaS platform. You'll own features from concept to production, building dashboards, billing UIs, and developer-facing tools while focusing on the developer experience.

You'll work with Ruby on Rails and React, move across the stack, and communicate timelines proactively. This role is embedded with the Monterail Tech Network on a client project.

Qualifications

• Fullstack engineer with Ruby on Rails and React proficiency.
• Strong focus on developer experience in tools you build.
• Comfort with ambiguity and owning features end-to-end.
• Proactive communicator who meets commitments and flags risks early.
• Experience with AI coding assistants is a plus.
• Design and UX sensibility in product flows.

Responsibilities

• Take features from concept to production, including dashboards, billing UIs, and developer-facing tools.
• Propose solutions and drive outcomes rather than waiting for a roadmap.
• Collaborate with clients and Monterail team on delivery and quality.
• Own quality and metrics post-release and iterate based on feedback.

Skills

Ruby on Rails

React

TypeScript

Developer Experience

Ambiguity Tolerance

Ownership

Proactive Communication

AI Coding Assistants

Tools

PostgreSQL

Node.js

TypeScript

Job description

Location: Remote · Collaboration: Freelance, via Monterail Tech Network · Start: ASAP

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.