I have been working professionally since 2017 in a variety of domains - energy and utilities, e-commerce, fintech, social networking, automated guided vehicles (AGV) - solving diverse problems in projects of all sizes and complexity levels. Backend & infrastructure are my main focus and strength, but I was also involved as a fullstack web and mobile developer; I enjoy being versatile and taking end-to-end responsibility. I am always interested in the following questions:
How the system works as a whole? What is its role and purpose? What value does it provide?
To have them answered, my curiosity often drives me to go beyond the currently assigned role. I truly love my work and care deeply about delivering the best possible solutions - taking the specific circumstances and context of the system into consideration.
Most of the projects I was engaged in were web-based and available through the browser, so that is the platform I know best. But, I have also worked on native mobile apps; I even did some embedded development (though still in Java) for the autonomous forklift project.
Below is a more detailed description of my work, experience and projects I was/am involved in:
Since 2026.02, I have been working at Jit Team, on a greenfield project for Allegro, a major e-commerce player in Poland. I am also involved in recruiting new developers, veryfing their skills and knowledge.
As of now, I am not allowed to describe what exactly the project is about, but my role is quite broad: including architecture design, refining requirements, technical implementation, as well as maintenance and development on production.
Tech stack: Microservices & Modular Monolith, Java, Spring Boot, MongoDB, Testcontainers, GitHub Actions, GCP, BigQuery, Kafka, Grafana and VictoriaMetrics (Prometheus-compatible).
Through 2025.01 - 2025.11, I was working on an internal invoicing & billing system for Respect Energy, a renewable energy company. The software mainly calculated client receivables, payables and final balances; it also issued various accounting documents - invoices, accounting & interest notes, compensations and so on. The domain was remarkably complex, involving numerous interconnected business rules and edge cases.
Major challenges:
As a senior developer, my responsibilities consisted of designing and proposing new solutions, aligning with other teams, specifying requirements more precisely, implementing them technically and guiding more junior team members. In this role, I have worked across the entire stack: backend, frontend and infrastructure (AWS). For some time, I was also involved in recruiting new developers and running a company-wide technical guild, which helped me to hone my soft skills.
Tech stack: Microservices, Spring Boot, Java, Hibernate, PostgreSQL, Apache Kafka and Avro, Testcontainers, Snowflake, Kubernetes, Argo CD, GitHub Actions, AWS, Microfrontends, TypeScript and React.
For the 2022.10 - 2024.12 period, I was involved in building a custom advertising system for the Modivo e-commerce platform, operating in multiple European countries under two brands - Modivo & eobuwie. It allowed the creation of paid campaigns that were then emitted on websites and apps belonging to the Modivo brand.
Major challenges:
Working in a small team of a few people, I was responsible for delivering features end-to-end: from refining requirements, organizing work through tickets & tasks to designing technical solutions and the actual implementation. It was one of the very best experiences of my career - I got to be at the very start of the product & system design, be involved in the technical implementation and then maintenance and evolution on production.
This is how it looked.
As a side quest, at the end, I worked on an interesting proof of concept: let's create a product search based on image and/or text description, using vector embeddings. The results were very promising, but due to structural changes in the company, the project was unfortunately shut down. Nevertheless, at the time I became more interested in the topic of vector embeddings - even making a YouTube video about it.
Tech stack: Microservices & Modular Monolith, Kotlin, Spring Boot, Spring Data JDBC, PostgreSQL, Testcontainers, GCP, Google Cloud SQL, BigQuery, Google Cloud Pub/Sub, Protocol Buffers, Apache Kafka, Kubernetes, Argo CD, Terraform, GitLab Pipelines, Grafana, Prometheus, Keycloak, TypeScript and Vue.js.
In the short span of 2023.04 - 2023.06, together with my brother, we designed and implemented the idea of a third Co-Founder - business speed dating app, allowing hosting online events for networking purposes.
Major challenges:
Sadly, due to personal problems of the third Co-Founder, the project was not fully launched - we only ran a few test events. But technically, it was ready to be used with the established date of the first official event.
This is how it looked.
A lot of technology that we - me and my brother - have designed and implemented while creating Hairo (especially around video calls) was reused here. Tech stack: Modular Monolith, Java, Spring Boot, PostgreSQL, Testcontainers, WebRTC, Coturn, Docker, Prometheus, Grafana, Python/Bash scripts, TypeScript and Vue.js.
From 2022.04 - 2023.05 I was building - together with my brother - Hairo: automated system for meeting new people.
Major challenges:
There were only two of us, working on everything - design, marketing, technical implementation as well as customer support. This was truly a life-changing experience and the deepest form of learning: I got to be a marketer, product owner and customer assistant while being architect & developer at the same time. After a year of its publication and gathering close to 1500 users, we decided to archive Hairo on May 31, 2023.
This is how it looked.
Tech stack: Modular Monolith, Java, Vert.x, PostgreSQL, Testcontainers, WebRTC, Coturn, WebSockets, RabbitMQ, Docker, Grafana, Python/Bash scripts, TypeScript and Vue.js.
Through 2021.11 - 2022.03, I was working on Uncapped products, both internal and client facing. They had/have a platform that allowed entrepreneurs to take loans without giving up equity and by repaying them proportionally to their revenue. I focused mostly on the backend and infrastructure, but from time to time I was also implementing some small UI changes.
Major challenges:
Tech stack: Microservices, Java, Spring Boot, jOOQ, Postgres, Testcontainers, GCP, Google Cloud Pub/Sub, BigQuery, Kubernetes, Flux CD, Terraform, Grafana, Prometheus and React with TypeScript.
In the 2019.11 - 2021.10 period I was a Java/Python programmer at Hycom. I mainly worked on a data lake platform for Fortum (energy company) that collected, aggregated, analyzed and visualized electricity, water and heat data from various meters.
Major challenges:
I was involved in a variety of things here: from implementing various Java and Python applications that were transforming and/or sending data to CI/CD improvements and then complete redesign of the process. Later on, I also became responsible for production releases, which I regularly carried out together with a DevOps engineer. On top of that, I participated in a project that made some of our data available through a dedicated REST API and UI.
As a side quest, together with a colleague I mentored a group of students for one semester. Under our wings, they were developing a real application that was later on presented at their university.
Tech stack: Java, Spring Boot, jOOQ, Postgres, TimescaleDB, Testcontainers, Python, Apache Parquet, Spark, Jenkins, Ansible, Grafana and lots of AWS services: ECS, S3, SNS, SQS, RDS, Secrets Manager, CloudWatch, CodeBuild, Athena, DynamoDB and CDK.
This was my first programming job, where I spent 2017.09 - 2019.10 period (from 2017.07, if internship is taken into account). At the time, it was a small software house and it was a great first experience and opportunity to learn - I worked on a few completely unrelated projects throughout those two years.
Firstly, I delved into developing native android applications in Java and Kotlin - for private clients as well as government institutions. Then, I worked on REST APIs, in particular on a tool for finding/planning a route based on an address and/or stops for public transport carriers. Later on, I was involved in developing algorithms for the autonomous forklift project - taking regular forklifts and making them autonomous by the use of our own software and custom hardware.
Tech I worked with here: native android development, Java/Kotlin, Spring Boot, SQLite, Postgres, Robot Operating System (ROS), network programming over UDP and TCP, Java Swing (GUI) as well as figuring out various new algorithms for the autonomous forklift project.
In a random order: