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Software Studio · Kraków, Poland

We build full-stack web apps and the products around them.

Assistars is a software studio building web applications end-to-end — from architecture to production. Founded and run by Leszek Słonczyński, with 15+ years of engineering behind it — from company websites to highly interactive web apps to AI-powered products.

Work with us See our products

Kraków, Poland · Remote

What we do

Senior engineering, from first commit to production

We take products from idea to something real people use — architecture, implementation, and the unglamorous work of getting them stable in production. You work directly with a senior engineer, not a layer of account managers.

01

Full-stack web development

End-to-end web apps: clean front ends, solid APIs, sensible data models, and the deployment to run them reliably.

02

Product engineering (0 → 1)

Turning an idea into a shipped product. Fast, focused iterations that reach real users instead of staying in a slide deck.

03

LLM / AI integration

Bringing large language models into real applications — thoughtfully, with an eye on cost, reliability, and genuine usefulness.

04

Technical consulting & architecture

A senior pair of hands for architecture decisions, code review, and untangling systems that have grown complicated.

How we work

  • Senior and autonomous — we own problems end-to-end.
  • We ship to production, not just to a demo.
  • Clear, low-noise communication.
  • Remote-friendly, flexible engagements.

Engagements

Flexible ways to work together.

Contract Project-based Advisory
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Products

Things we have built and are building

Software we design, build, and run ourselves — not just client work.

Assistars — the platform

LIVE

Run your business from one place.

A cloud SaaS for small businesses: CRM and a sales pipeline, invoicing and documents, cash-flow tracking, team and time management, warehouse and orders, and business analytics. In production with real users.

CRM & sales pipeline Invoicing & documents Cash flow & finance Team & time tracking Warehouse & orders Analytics

Live product · ask us for access

See the platform

Aurelian

COMING SOON

Your personal AI taste curator.

An AI companion that learns what you love across films, TV, games, and books — from the way you already talk about them — then reaches across an LLM’s knowledge and live sources to recommend what is genuinely for you. Private, invitation-only, and built to remember only what you actually tell it.

AI / LLM-powered Films · TV · Games · Books Learns from conversation Private & invite-only

Coming soon · private beta

About

The engineer behind Assistars

Assistars is a one-person studio by design — you work directly with a senior engineer instead of a chain of hand-offs. For 15+ years I have built full-stack web applications end-to-end, most recently LLM-powered products, both on my own products and inside engineering organisations.

Highlights

  • Full-stack web application development for 15+ years.
  • Founder-engineer: designing, building, and running my own SaaS products.
  • Experience inside engineering organisations, including Software Mind.
  • Years of hands-on delivery and Scrum leadership — for when a build needs steering, not just code.

Certifications

  • Claude Certified Architect — Foundations (Anthropic)

Toolbox

TypeScript JavaScript Angular React Node.js REST APIs SQL / Databases Cloud & DevOps LLM / AI integration System architecture

Contact

Have a project or a role in mind?

Tell us a little about what you are building or the help you need. Every message reaches Leszek directly, and gets a personal reply.

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Kraków, Poland · Remote