What Sintra is building

Sintra is building AI Employees for more than 50,000+ small business owners worldwide. From social media, sales, recruiting, support and more. An intuitive & easy way to run automations, complete tasks and generate ideas. With integrations to Facebook, Instagram, Linkedin, Google Drive, Calendar, Mail, Outlook and Notion.

We've launched the v1 of the product on May 15th, 2024 and ever since then we've had crazy traction – by becoming one of the fastest growing new AI startups in Europe.

We believe the product is still in its infancy and there's so much more to build.

About Sintra as a company

⭐️ Small team. Our aim is to keep the team as small and as lean as possible with the best people that we can find. We believe in hiring less, but hiring better. We also look for the right culture and value fit. This enables us to move faster and work closer.

🫠 Not a 9-5. Building a startup is hard. Building a great startup is even harder. We want to build a generational company that we'd want to work in, and that our friends would want to work in.

✨ Close environment. You'll work directly with founders day-to-day and build the company with us. We have daily lunches with the entire team (covered by us).

💪 Freedom. Lots of freedom here — but that means lots of responsibility, too. No micromanagement, just trust and autonomy.

🙏 Care. We've actually visited our customers in person, making real-life documentaries with them and hearing out their stories. Each customer we serve is an actual human, not just a big enterprise, and that keeps a lot of why we do what we do.

Read more about what the culture at Sintra is like.

We’re looking for a curious and detail-driven Prompt Engineer who loves working with Large Language Models and improving how they perform in real-world products. You’ll work directly with sintra.ai system to design, test, and optimize prompts, explore new LLM capabilities, and help elevate the quality of our platform’s AI output.

🛠 Responsibilities:

Design, test, and optimize prompts for various use cases across the Sintra platform
Run LLM evals to compare model behavior, track improvements, and identify regressions
Build and maintain eval datasets to support consistent, measurable prompt quality
Research LLM capabilities, best practices, and emerging techniques to improve model performance
Run structured experiments, analyze results, and iterate on prompt strategies
Collaborate with product, engineering, and data teams to implement prompt improvements
Document prompt workflows, evaluation results, and experimental findings
Identify edge cases, inconsistencies, and opportunities for improving AI responses
Ensure prompts align with user experience, accuracy, and safety standards

🎯 Requirements:

Extensive experience working with Large Language Models (prompt engineering, fine-tuning, workflow testing, or similar)
Strong analytical and problem-solving skills with attention to detail
Technical aptitude - comfortable working with structured tools, APIs, or testing environments
Ability to run systematic experiments, LLM evals, and interpret model behavior
Experience or interest in building evaluation datasets
Excellent written communication skills (English)
Creative mindset for designing effective prompts and testing new approaches
Self-driven, curious, and able to work autonomously in a fast-paced environment

🙌 About our perks:

Compensation & Equity: Top-of-market salary in Vilnius plus meaningful equity, so that you own a part of what you build. Salary range for this role is €3,500-5,000 EUR gross / month depending on expertise and experience.
Health & Wellness: Health insurance, gym membership with personal trainer option, team lunch at the office.

Sintra

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Prompt Engineer