Available for new projects

Senior Backend Engineer · Python & AI

Writing code is no longerthe hard part.

Systems thinking and understanding the domain matter more than ever. 6 years on SaaS products: backends, data acquisition and AI-backed features. Let's build something stable and scalable together.

Working with
  • Python
  • Django
  • FastAPI
  • PostgreSQL(+pgvector)
  • Next.js

Products I've built and shipped

Stack & expertise

The toolkit behind the products

Backend-first, comfortable across the stack. I pick boring, proven tools and make them ship outcomes.

01

Backend

  • Python
  • Django / DRF
  • FastAPI
  • Flask
  • SQLAlchemy
  • Pydantic
02

Data & storage

  • PostgreSQL + pgvector
  • BigQuery
  • Redis
  • MySQL
03

Messaging & streaming

  • Kafka
  • RabbitMQ
  • Celery
  • asyncio
04

AI & agents

  • LangChain
  • LangGraph
  • Agentic workflows
  • RAG
  • Claude Code
05

Infrastructure

  • Azure
  • GCP
  • AWS
  • Terraform
  • Docker
  • Linux
06

Frontend

  • React
  • Next.js
  • TypeScript
About

Backend engineer focused on what code generation won't solve.

6 years of backend work on SaaS products, in fast-paced startups and in larger companies, across HR, AdTech, AI search and GEO, fraud detection and telecom. One thread runs through all of it: data acquisition. Crawlers, ETL pipelines and custom collection mechanisms for domains with no reliable structured source, from advertising fraud traffic to the answers generative AI gives about a brand.

AI coding tools are part of how I work every day, and I am deliberately growing into AI engineering. As code generation gets cheaper and faster, the bottleneck moves elsewhere: designing systems that hold together, understanding the domain well enough to know which problem is worth solving, making the right architectural trade-offs.

I hold a high bar for quality. Clean architecture, meaningful tests, readable code and performance that survives real load, because that is what keeps a system cheap to change a year from now.

Services

How I can help

Engagements built around shipping software outcomes - not billing hours.

01

Backend systems

APIs, data models, async workers and the unglamorous plumbing that keeps a product reliable as traffic grows.

02

Data acquisition

Crawlers, ETL pipelines and custom collection mechanisms for domains with no reliable structured source, turned into a dataset you can actually query.

03

AI features

LLM-backed features and agentic workflows on LangChain and LangGraph, with retrieval over your own data so answers come from your catalog, not from model memory.

04

API design

Versioned, documented, well-tested REST APIs that frontend teams and integrations actually enjoy using.

05

Performance & quality

Query and endpoint optimisation, test coverage that catches regressions in CI, and refactors that make a legacy codebase safe to change again.

06

Technical consulting

Architecture reviews, stack decisions and pragmatic guidance for teams scaling a Python codebase.

Selected work

A few things I've built

Project teardowns: the problem, the stack and the outcome.

Side projects

Building to learn

Loose, educational projects - I build them to get hands-on with a new technology or to crack a specific problem.

Mieszko previewML

Mieszko

Asking-price valuation for flats in Rzeszów - an ML model trained on sale listings from the city. From the address alone it enriches each record with a dozen extra location features generated from OpenStreetMap. Validation MAPE 6.7%, against 15.5% for a naive baseline.

  • Python
  • XGBoost
  • FastAPI
  • OpenStreetMap (Overpass)
  • Leaflet
  • Docker
A price from four fields
Mandaflix previewAI · ML

Mandaflix

A streaming-style movie recommender with two independent AI systems: personalised recommendations and hybrid semantic search, behind a Netflix-like UI that hides the algorithms.

  • Python
  • FastAPI
  • scikit-learn (SVD)
  • Postgres + pgvector
  • React + Vite
  • Docker
Recommendations + hybrid retrieval
LLM · IoT

Voice-controlled home

Control your home by voice over Telegram, in plain Polish and with your own device names. A voice note is transcribed, an LLM turns it into a structured intent, and the system flips the relay locally over the LAN - with a hard guarantee it can't invent a device that doesn't exist.

  • Python 3.12
  • Groq (Whisper + gpt-oss)
  • python-telegram-bot
  • Shelly Gen3 RPC
  • Docker
Talk normally, the house listens
Contact

Let's build something worth shipping.

Got a backend that has to scale, data with no clean source to pull it from, or an AI feature that has to be trustworthy? Drop me a line.

hi@krystianjarmul.dev

or find me on