Senior Backend Engineer, Bïrch

• We're looking for a senior engineer who combines technical depth with a product mindset — someone who cares about the "why" just as much as the "how". You're comfortable owning complex systems and making architectural decisions on your own. You find smarter, simpler ways to solve problems instead of over-engineering, and once the team makes a call, you stand behind it fully
• You have deep expertise in Ruby and Ruby on Rails. You understand how the framework works under the hood, keep up with new versions, and write clean, idiomatic code
• You're confident with Go. Our backend is a dual-language architecture: a Rails monolith for the web app and 20+ Go microservices that power our core automation engines, APIs, and heavy processing. You'll work across both daily roughly 50/50
• You have expert-level knowledge of PostgreSQL. Not just writing queries, but understanding how databases work at scale: indexing strategies, query optimisation, partitioning, and knowing when scaling techniques are needed
• You have a DevOps mindset. You take responsibility for how your code runs in production and can make infrastructure-related decisions. Our infrastructure is deliberately simple: EC2 instances, Docker containers, Terraform and Ansible — no Kubernetes, no serverless. Engineers own how their code runs
• You have a pragmatic relationship with AI tools. You use them when they help you move faster, understand what the AI produces, and know when it’s quicker or safer to just write the code yourself
• You take testing seriously — writing effective tests that cover essential scenarios without unnecessary overhead
• You're skilled in performance optimisation — you use caching, specific algorithms, or architectural patterns when they bring real, measurable benefits
• You primarily communicate in English with your teammates

Desirable

• You’ll be the sole backend engineer in a small product squad, working alongside a product manager, a frontend engineer, and a product designer, with full ownership of the backend side. Our platform handles billions in ad spend across Meta, Google, TikTok, and Snapchat, so reliability and quality of your work have a direct financial impact
• Our stack is Ruby on Rails 8 and Go 1.25, with PostgreSQL 18, Redis, Sidekiq, and Docker under the hood. We deploy via GitHub Actions and monitor with Grafana, Prometheus, and Sentry
• Own large features and full products. You'll be the primary backend engineer taking features from idea to release — working closely with product manager, designer and your frontend counterpart
• Write production-ready code in Ruby and Go for new features and products, as well as improving existing systems
• Proactively find high-value work and help guide the team's planning process. Participate actively in product planning, contributing to defining how technical problems should be solved
• Handle and triage production issues across different systems, taking ownership and driving them to resolution
• Review critical pull requests and give clear, actionable feedback aligned with our engineering principles
• Develop and maintain integrations with ad platforms like Meta, Google, TikTok, and Snapchat APIs — each with their own data models, rate limits, and quirks
• Define and improve engineering standards — from coding and testing practices to monitoring, debugging workflows, and CI/CD pipelines

• 1. Submit your application 2. Screening interview with Aleks, People Generalist 3. Interview with CTO and Backend Engineering Lead 4. Live-coding interview 5. Test day in Barcelona. If not possible to travel, virtual coffee with the team.