Senior Full-Stack Engineer

Why Sintra?

50,000+ small business owners use Sintra every day. Not because it's another SaaS tool — but because our AI helpers actually feel like teammates. They reply to customers, post on social media, analyze data, and much more. For someone running a business alone, this is the first time they've had help that actually helps.

We've built something people care about. Now we need to make it great.

Quick summary: We’re looking for a full-stack engineer who can own features end-to-end. You’ll build core product functionality at Sintra - shaping how AI helpers behave and implementing the backend logic and frontend experiences that make it useful for real users. The challenge: making AI-driven workflows reliable and predictable, while keeping the experience simple for non-technical users. You’ll ship across the entire stack with a focus on clean, maintainable code and systems that handle edge cases well.

What you'll do

• Build core product features that define how users interact and collaborate with AI

• Create tools/functions that LLMs can reliably call - with bulletproof error handling and clear documentation

• Develop frontend interfaces that make complex functionality simple for non-technical users

• Design and build workflows that combine multiple operations into cohesive product features

• Ensure reliability through solid error handling, retries, fallbacks, and predictable system behavior

• Instrument everything - add logging, tracking, and metrics to understand real usage and iterate based on data

• Collaborate with designers on both user experience and technical constraints

• Mentor teammates and raise the engineering bar through code reviews and pair programming‍

• Who we're looking for

• 4+ years shipping production full-stack applications.

• Strong Typescript, Node.js, and React skills with focus on clean architecture.

• Experience with LLM tool calling, function definitions, and prompt engineering.

• Solid product thinking - you understand how technical decisions affect user experience.

• Comfortable navigating large codebases and understanding service boundaries.

• Track record of shipping independently while collaborating well with designers and other engineers.

• Strong code review skills - you catch bugs before they hit production.

• Comfortable using AI tools to accelerate development.

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• Our tech stack

• Frontend: React

• Backend: Typescript, Node.js

• Infrastructure: Railway, AWS, multiple LLM providers

• DevOps & Tooling: Github Actions, Grafana

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• Salary range: €5,000-8,000/month gross, depending on experience.

Benefits

• Equity package: share in the company’s long-term success through an equity plan that rewards your impact and commitment.

• Flexible working model: enjoy a flexible approach to work that supports a healthy balance between your professional and personal life.

• Private health insurance: comprehensive private health coverage to support your well-being.

• Workout sessions with a personal trainer: access guided workout sessions with a personal trainer to help you stay active, healthy, and motivated.

• Daily office-provided lunch: fresh, complimentary lunch provided in the office every workday to keep you energized and focused.

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