Back-End Developer

12 липня 2026

Back-End Developer

Вінниця, Варшава (Польща), віддалено

Fit4Me is looking for a  Middle Back-End Developer who will help build and scale the backend of our Health & Fitness product, creating server-side solutions that directly impact user personalization, product stability, and the speed of delivering new features.

One of the key focus areas of this role will be developing backend services, the admin panel, and internal tools that power content management, personalized workout programs, and the core business logic behind our product.

You will work on functionality that allows users to personalize their workout experience by customizing exercises, reordering workout flows, switching between personal plans, and interacting with the product in a more flexible way. You’ll also contribute to the evolution of our backend architecture, integrate new services, and continuously improve our technical platform as the product grows.

This role is a great fit if you:

• Want to build functionality that directly impacts the experience of thousands of users.
• Enjoy working with business logic, APIs, and backend architecture.
• Thrive in a product team where ownership, autonomy, and responsibility are valued.
• Like designing clean, maintainable, and scalable backend solutions.
• Want to see how your technical decisions contribute to product growth.

Your area of Impact:

• Develop and maintain backend functionality for our mobile product, admin panel, and internal services.
• Build and support REST APIs for the mobile application and internal tools.
• Develop features that power workout personalization, content management, and user journeys.
• Design new data models, extend business logic, and improve the existing backend architecture.
• Work with MongoDB (Mongoose), PostgreSQL, and Redis.
• Build integrations with external services, webhooks, and AWS.
• Manage file storage and media assets using AWS S3.
• Implement and maintain secure authentication and authorization mechanisms using JWT and OAuth.
• Optimize database performance, improve query efficiency, and contribute to data migration between different storage solutions.
• Collaborate closely with Product Managers, Designers, and Engineers to deliver new product capabilities.
• Contribute to technical documentation and continuously improve backend architecture and engineering practices.

Tech stack: Node.js, TypeScript, PostgreSQL, MongoDB, Redis, REST API, Swagger / OpenAPI, AWS, JWT / OAuth, Git.

What do you need to join us:

• 3+ years of commercial experience as a Back-End Developer.
• Strong hands-on experience with Node.js and TypeScript.
• Practical experience working with MongoDB and Mongoose.
• Experience with PostgreSQL or other relational databases.
• Experience working with Redis.
• Hands-on experience building and maintaining REST APIs.
• Understanding of scalable backend architecture principles.
• Experience integrating external services and working with webhooks.
• Solid understanding of authentication and authorization mechanisms (JWT, OAuth).
• Experience working with AWS (experience with AWS S3 is a strong plus).
• Experience using Git in a collaborative development environment.
• Understanding of clean architecture principles, REST, and SOLID.
• Ownership mindset, analytical thinking, and the ability to work independently.

Nice to have:

• Experience working with RabbitMQ or other messaging/queue systems.
• Experience using Docker.
• Hands-on experience with Swagger / OpenAPI.
• Understanding of ACID principles and database transactions.
• Experience working with ORM frameworks such as TypeORM, Sequelize, or similar.
• Experience participating in database migration projects between MongoDB and SQL.
• Experience working with payment systems, subscriptions, billing, or financial integrations.
• Experience building backend systems for mobile products.
• Understanding of logging, monitoring, and basic observability practices.

What we offer:

• Fully remote work with a flexible schedule and dedicated business hours for collaboration.
• A high level of autonomy, trust, and ownership over your work.
• The opportunity to contribute to a Ukrainian Health & Fitness product that helps people build healthier lifestyles.
• A collaborative team that values open communication, fast decision-making, and initiative.
• Opportunities for professional growth while working alongside an experienced product and engineering team.

If this role sounds like a great fit for you, we’d love to hear from you!

Please send us your CV and include a short answer to one question in your application:
What are the request and response objects in Node.js, and how are they related to streams?

Hiring process:

Interview with Recruiter → Technical Interview → Final Interview with HRD → Job Offer

About Fit4Me

Fit4Me is a Ukrainian product startup founded in 2023, creating a personalized Health & Fitness products for a global audience. Our app combines and adapts multiple fitness directions to individual user needs. We are profitable and operate with a fully remote team of 50+ specialists worldwide.

Our mission — Fit your dream.
We believe a healthy lifestyle should feel easy and enjoyable, so we focus on helping users build sustainable habits through positive, motivating experiences.

Our principles

Startup speed — we test ideas in days, not months.
Performance first — measurable results matter more than perfect plans.
Fast decision-making — direct access to  C-level and product leadership.
Autonomy equals responsibility — freedom without micromanagement.
Real impact — your work helps people change their lives for the better.

Fit4Me is for those who:

• Want to build products that genuinely change people’s lives.
• Value speed, autonomy, and direct communication.
• Are ready to take ownership and act proactively.
• Want to work in an environment of driven people where everyone strengthens the product and the team.

What we offer

Fast learning as part of our DNA — monthly internal workshops (from hard skills to life hacks), sessions with team leads and external experts, plus a learning budget for courses and conferences.

Remote with trust — core sync time is 10:00–18:00 Kyiv time; the rest is up to you. We focus on results, not hours in Slack.

⚡ Career boost — fast and transparent growth in roles and responsibilities. Internal candidates are always a priority.

Wellbeing — flexible time off, regular recovery days, weekly optional meditation sessions, 14 vacation days, unlimited sick leave.

Ready to build products that change lives?
Join Fit4Me

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