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Marcin KrężelBook a call

I automate repetitive work in your business – from idea to a working tool

I’m Marcin, a freelance software engineer. I take ownership of the whole thing – from talking through the problem, through choosing the technology, to deployment and documentation.

Book a free callSee projects

Software agency? See how I can deliver a module for your project

Example: handling orders from email (indicative numbers)
  1. Reading the order from the email4 min
  2. Copying the data into a spreadsheet6 min
  3. Sending a confirmation to the customer3 min

13 min × 40 orders a week = 8.7 h by hand

After automation: 8.7 h a week back to your team

The tool reads the email, fills in the spreadsheet and sends the confirmation. A person only checks the exceptions.

What I can do for your business

I start with the problem, not the technology. I pick tools that fit what already works in your company – and if AI is not the best answer, I will say so.

  • Process automation

    Someone copies data between systems by hand or collects it from websites.

    Integrations and workflows that run unattended – including scheduled data collection from the web – and alert you when something goes wrong.

    Python, n8n, API, AWS, Playwright

  • AI agents and chatbots

    Your team answers the same questions over and over.

    A chatbot or agent that answers from your own documents (RAG) and works inside the tools you already use.

    LangChain, LangGraph, OpenAI / Claude API

  • Web applications

    The business runs on spreadsheets and email instead of a proper tool.

    A backend, API and admin panel or dashboard shaped around how your team actually works.

    FastAPI, Django, PostgreSQL

End-to-end project for small businesses. From talking through the problem to deployment and documentation. A fixed price for the whole project or per milestone.

Subcontracting for software agencies. A self-contained module – an AI agent, an integration, an automation – in your repository and your process, under NDA.

You get a proper invoice. We agree on billing during the first call.

Selected projects

No client names – some projects are under NDA. The industries and numbers are real.

SaaS platform for sales team training

Sales reps learn their sales process with an AI assistant and practise calls by voice

Problem
Companies described their sales process on the platform: stages, scripts and objections. The client wanted that knowledge to work for the sales reps: answer questions, teach new hires and let them practise conversations with a customer.
Solution
An AI service with an assistant that answers questions and teaches the process in text and by voice, and a trainer that lets reps practise a conversation with a simulated customer. Managers get a summary of each rep's progress.
Result
The voice trainer responds more than twice as fast as in the first version. One service handles many companies in two languages.

Python, FastAPI, LangGraph, LLM, Text-to-Speech

See details for Sales reps learn their sales process with an AI assistant and practise calls by voice →

SaaS platform for B2B sales teams

Personalised LinkedIn messages in seconds instead of writing them by hand

Problem
B2B sales reps spent hours writing messages that still sounded like a template.
Solution
An AI tool writes a message for a specific person and company, taking the seller's offer into account, and learns from the messages users approve. It also helps choose which companies and roles are worth contacting.
Result
A message tailored to the recipient in a few seconds, for many companies using the platform at the same time.

Python, FastAPI, LangGraph, LLM, PostgreSQL

See details for Personalised LinkedIn messages in seconds instead of writing them by hand →

Sales company in the energy sector

Leads in one system, while sales reps keep working in their calendar

Problem
Leads came in from several channels into spreadsheets and were passed on by hand. There was no single place showing who handles a client and what stage the conversation is at.
Solution
A CRM collects leads from different sources, assigns them to sales reps and books meetings in their Google Calendar. Reps update the status in the calendar, and the CRM picks up the changes on its own. A Make integration connects the CRM with the company's internal automations.
Result
A single source of truth for leads, with full history. Sales reps don't have to log in to yet another system.

Python, Django, PostgreSQL, Google Calendar API, Make

See details for Leads in one system, while sales reps keep working in their calendar →

All reviews on Useme (in Polish)

How I work

  1. Step 1

    Free call

    30 minutes. You tell me how the process works today, and I keep asking until I understand the problem.

  2. Step 2

    Quote and scope

    You get a description of the solution, the proposed tools and a fixed price – for the whole project or per milestone.

  3. Step 3

    Build

    I work in short iterations. After each one you see working progress, and automated tests make sure nothing breaks.

  4. Step 4

    Deployment and documentation

    I set the solution up on your side, hand over the documentation and stay on for a support period.

Marcin Krężel – portrait photo

About me

I’m Marcin – a software engineer and AI engineer. For 6 years I have been building backends, integrations and automations in Python, and more and more often AI solutions that businesses use every day.

I help companies get rid of repetitive work: I connect systems that don’t talk to each other and bring in AI where it genuinely saves time.

I’m also QA at heart – I have hands-on experience in test automation, so I treat quality as part of the product, not a final step. Tests, edge cases and what could go wrong are on my list from day one.

I have worked with small businesses and in teams building SaaS products.

I work remotely, document what I deliver, and say so plainly when AI is not the right answer.

Tools I reach for most often

  • Python
  • FastAPI
  • Django
  • LangGraph
  • OpenAI / Claude API
  • PostgreSQL
  • Celery
  • pytest
  • Docker
  • n8n
  • AWS

GitHubLinkedInUseme profile

Tell me what you want to improve

A few sentences are enough. I will reply within 1–2 business days and suggest a time for a free call.