Senior Backend Engineer

We are currently seeking an experienced Senior Backend Engineer to join our team in support of our US-based partner company. Our partner operates a diversified, M&A-driven platform spanning mobile apps, device licensing, media, and financial services. It is the parent company of a portfolio of technology businesses, including a mobile business that empowers users worldwide to monetize everyday mobile activities such as streaming, gaming, and shopping.

As a Senior Backend Engineer, you will help build, scale, and evolve the backend systems powering our consumer-facing mobile products. You’ll architect reliable services, increase speed and resilience, optimize infrastructure, and unlock new features that help users achieve goals and earn points more effectively. You’ll architect reliable services, increase speed and resilience, optimize infrastructure, and unlock new features that help users achieve goals and earn points more effectively.

This is a hands-on, high-impact role ideal for someone who loves solving complex systems problems, building scalable APIs, and shipping features that directly impact product performance and user experience. You will collaborate closely with product, design, data, and frontend engineering to deliver features through rapid development cycles and deployment.

Responsibilities:

Build & Scale Core Services

• Architect backend systems powering user workflows, notifications, and automation features
• Design APIs and microservices built for performance, efficiency, and scale
• Quickly learn and apply new technologies as needed
• Work with high-volume data systems and event-driven architectures
• Improve observability, monitoring, logging, testing, and alerting
• Identify performance bottlenecks and implement optimization strategies
• Build distributed systems with multiple services, queues, external APIs, and asynchronous data flows
• Ensure uptime, stability, and production resilience
• Build resilient integrations with third-party services
• Work in 2-week sprints with CI/CD and strong code quality practices
• Partner with product, data, and frontend to ship features
• Participate in system design and architecture reviews
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Qualifications:

• 6+ years of backend engineering experience, ideally in consumer apps, mobile, or SaaS, with at least 2 years in a senior-level role
• Expert-level proficiency in Ruby on Rails, including modern versions and best practices (this is central to the role)
• Hands-on production experience with PostgreSQL, including schema design, indexing strategies, query optimization, and performance tuning
• Strong expertise with Sidekiq for background job processing, including scheduling, throttling, batching, and reliability patterns
• Proficiency using Redis for caching, job queues, and distributed locking
• Experience with DynamoDB or comparable NoSQL databases
• Solid background in API design, RESTful principles, versioning, and serialization
• Proven track record of integrating with third-party APIs and external services
• Experience designing, building, and scaling distributed systems in production
• Familiarity with AWS services, including S3, DynamoDB, SQS, CloudWatch, and SES
• Strong skills in testing, CI/CD pipelines, logging/monitoring, debugging, and performance optimization
• Ability to work in a fast-moving remote startup environment

Preferred

• Experience building and supporting backends for mobile apps
• Experience creating internal tools or admin panels with ActiveAdmin
• Hands-on work with Shoryuken for SQS message processing
• Experience integrating payment processors like Stripe

Nice to Have

• Event-driven or streaming architecture
• AI-assisted/AI agentic development (GitHub Copilot, Cursor, Claude Code, Codex, etc.)
• Feature flagging, experimentation, or A/B testing

We offer:

• Full-time, remote work
• Working hours: Monday to Friday, start from 11am CET or later
• Private health insurance from day 1
• Timely and organized performance reviews

If this seems like the right job for you, we invite you to submit your resume in English. Please keep in mind that resumes in other languages might not be considered.