Senior Back-End Developer (Health & Fitness App)
We are looking for a Senior Back-End Developer to join our partner team, who will own and scale backend systems powering our mobile and web products. You will be responsible for building and maintaining backend architecture that ensures reliable product performance across core functionality, payments, integrations, and internal tools. This role has a direct impact on system stability, scalability, and the ability of the product to grow without technical bottlenecks.
- Design and maintain backend architecture for the mobile product, admin panel, and internal services.
- Build and scale REST APIs, integrations with external services, payment platforms, and webhooks.
- Design data schemas, manage migrations, optimize queries, and improve database performance.
- Ensure system reliability and scalability: performance, fault tolerance, monitoring, logging, and alerting.
- Implement and maintain secure authentication and authorization mechanisms (JWT, OAuth).
- Collaborate with product and engineering teams to deliver and scale new features.
- Contribute to improving technical documentation and system architecture.
- 4+ years of production experience as a Back-End Developer.
- Strong hands-on experience with Node.js and TypeScript in commercial products.
- Experience working with PostgreSQL, MongoDB, and Redis.
- Proven experience building scalable and reliable backend systems.
- Experience developing REST APIs, integrations, and working with webhooks.
- Solid understanding of authentication and authorization (JWT, OAuth).
- Experience working with AWS or other cloud platforms.
- Experience working in production environments: logging, monitoring, incident handling.
- Ability to take ownership and deliver solutions end-to-end.
- Experience collaborating with cross-functional teams.
- Nice to have: Experience working with payment systems, billing, subscriptions, refunds, and chargebacks.
- Nice to have: Experience building backend systems for mobile products.
- Nice to have: Hands-on experience with rate limiting, idempotency, retry logic, queues / jobs.
- Nice to have: Experience with payment orchestration, CRM systems, or analytics services.
- Fast learning culture - regular workshops (from hard skills to life hacks), sessions with internal leaders and external experts, plus a learning budget for courses and conferences.
- Remote with trust - core hours 10:00–18:00 (Kyiv time), then full flexibility. We value results, not hours online.
- Career boost - fast, transparent growth in roles and responsibilities, with internal candidates always prioritized.
- Wellbeing support - 2 additional recovery days per month, optional weekly meditations, 14 days of vacation, and paid sick leave.
Boosta is an international IT company that develops and promotes SEO tools, digital products and educational products, primarily for Western markets. Founded in 2014 and headquartered in Kyiv, Ukraine, it has released more than 10 products used by tens of thousands of people across Europe, Asia, the Americas and Australia. The company employs a team of over 400 specialists and runs an R&D department that backs startups and develops new products. Boosta operates across several verticals, including the iGaming affiliate space.
