Senior Software Engineer

About Us Karla is transforming the post-purchase experience in e-commerce. Our platform helps online merchants turn delivery tracking into a revenue-generating channel while dramatically reducing customer anxiety and support costs. Founded in Berlin and backed by €3.4M in pre-seed funding, we're scaling rapidly across Europe. We integrate with 1000+ carriers and power millions of deliveries for hundreds of merchants. We're at an inflection point and looking for exceptional engineers to help us grow. About the Role We're looking for a Senior Software Engineer to join Karla’s engineering team and build end-to-end solutions that power the post-purchase experience for renowned international brands. As a Senior Software Engineer, you'll take ownership of complete features from conception to production. You'll leverage modern tools and AI-powered workflows to accelerate development while maintaining high-quality standards. You'll have the autonomy to architect solutions within your domain and ship code with confidence backed by comprehensive testing. We value engineers who can move quickly without sacrificing craftsmanship: those who know when to reach for AI assistance to handle repetitive tasks and when to dive deep into complex problem-solving. What You'll Do Build complete features end-to-end from database to user interface, owning the full technical stack. We use Python FastAPI in the backend, React/Next.js in the frontend, and Kubernetes for the infrastructure. Design and implement scalable systems that handle growth and complexity across all layers. Ship high-quality code rapidly by leveraging AI tools strategically for scaffolding, testing, and refactoring while maintaining craftsmanship for complex logic. Architect robust APIs and services that power seamless user experiences. Optimize system performance across the entire stack, from database queries to API response times to UI rendering. Collaborate cross-functionally with product and design to deliver cohesive solutions. Drive technical decisions within your domain, balancing pragmatism with long-term sustainability. Improve developer experience by championing better tooling, automation, and AI-augmented workflows. What Success Looks Like First 3 Months Ramp up quickly on our codebase, architecture, and development workflows, leveraging AI to explore and understand the systems faster. Ship 3-5 complete features to production, spanning multiple layers of the stack. Contribute high-quality code reviews with constructive technical feedback. Build strong working relationships across engineering, product, and design teams. First 6 Months Own end-to-end delivery of major features, from database design through API implementation to user interface. Drive meaningful improvements to system performance, reliability, or developer experience. Contribute to architectural decisions and influence technical direction. Become productive across the full stack, comfortable making changes anywhere in the codebase. First Year Be a go-to resource for complex problems spanning the entire system. Lead initiatives that significantly improve code quality, system architecture, or team velocity. Demonstrate consistent high output by effectively combining deep technical work with AI-augmented productivity. Operate autonomously with minimal guidance, making sound technical decisions that balance speed and sustainability. About You Experience & Technical Skills Extensive experience building production software across multiple layers of the stack in fast-paced environments. Strong in at least one modern language/framework (Python, TypeScript/Node.js, Go, etc.) with willingness to work across the stack. Solid foundation in system design, data structures, and algorithms. Experience with SQL databases (e.g. PostgreSQL, MySQL) and NoSQL (e.g. Redis, MongoDB) for data modeling and query optimization. Proficient with REST APIs and modern web technologies. Experience with GraphQL or frontend frameworks (React, Vue) is a plus. Comfortable with cloud platforms, containerization, and infrastructure. Engineering Excellence Writes clean, well-tested code with focus on maintainability and long-term quality. Works with AI to accelerate development, using assistants for scaffolding, refactoring, and testing while applying judgment for complex logic. Strong debugging skills across the full stack, from database queries to UI issues. Experience with comprehensive testing strategies (unit, integration, E2E) and maintaining high coverage. Proficient with CI/CD pipelines and confident deploying to production. Security-conscious with an understanding of common vulnerabilities and mitigation strategies. Ownership & Velocity Takes end-to-end ownership from requirements gathering through deployment and monitoring. Ships features rapidly without sacrificing quality by knowing when to use AI assistance vs. when to dive deep. Monitors production systems and proactively addresses issues before they impact users. Pragmatic decision-maker who balances speed, quality, and technical debt. Collaboration & Growth Works effectively across teams (product, design, sales…) and other engineers. Clear communicator who explains technical trade-offs in code reviews and design discussions. Breaks down complex problems into manageable pieces and unblocks others. Shares knowledge about modern development practices. Continuously learns and adapts to new technologies and workflows. The Benefits Impact Transform e-commerce at scale : Your code directly powers delivery experiences for hundreds of online merchants and millions of end customers across Europe. Reduce customer anxiety : Build systems that proactively keep customers informed, cutting "Where Is My Order?" inquiries by 60% and saving merchants up to 75% in customer service costs. Drive real business outcomes : Own features that turn post-purchase experiences into revenue-generating channels, directly impacting merchant growth and customer retention. Shape technical direction : At our stage (post-seed, scaling rapidly), your architectural decisions and technical choices will influence the platform for years to come. Growth Modern tech stack and AI-first workflows : Use cutting-edge tools and leverage the latest AI code models to build faster while maintaining quality. We use Claude Code extensively and continuously adopt tools that boost productivity Learn from experienced engineers : Collaborate with a team that values craftsmanship and continuous improvement. Work on complex, real-world problems : Multi-carrier integrations (1000+ carriers), real-time tracking at scale, distributed systems, AI-powered customer communications. Culture & Benefits Berlin-based, remote-first with flexible hours. Competitive salary and meaningful equity in a growing company. We prioritize learning over blame and feedback over hierarchy.