Sep 12 2025
JavaZone 2025 report
This is a summary of the JavaZone 2025 conference I attended in early September. It’s a conference focused on developers that I enjoyed and highly recommend.
Aug 6 2025
How the Garbage Collector Works in Go and How It Affects Your Programs
Have you ever wondered what happens with the variables you define in your Golang (Go) programs? Do they exist forever, or are they recycled at some point? Where do they live in memory and how are they managed?
Jul 14 2025
Popular Gradle mistakes (and how to avoid them) - part 3
In the previous post - part 2, we covered more common Gradle mistakes and how to fix them. In the last part of this triplet, we will share our favorite Gradle plugins that can help you avoid some of the mistakes we discussed in the previous posts!
May 27 2025
How to call a REST API in integration tests
Have you ever struggled to identify which REST API is being tested in your integration tests? In this article, you’ll learn a clean and readable way to call REST APIs within your integration tests. The goal is to make the WHEN section of the test clearly show which API is called and in what context, while hiding all technical details.
May 19 2025
Unlock faster data processing for Machine Learning: reducing pivoting time from hours to minutes
Training Machine Learning models on big data isn’t just about fitting the model itself — it’s about efficiency at every stage of the process. While much attention is given to optimizing model training itself, the earlier phases can be just as, if not more, critical to the overall performance. In this article, we take a deep dive into what happens before we actually invoke model.fit(), focusing on the data pivoting stage. We are taking you on a journey through various pivoting solutions, exploring both pitfalls and interesting optimizations. The goal is simple: make this process highly efficient — in terms of processing time and memory usage. So, buckle up!
May 5 2025
Popular Gradle mistakes (and how to avoid them) - part 2
In the previous post - part 1, we covered common Gradle mistakes and how to fix them. After a review and feedback from the community, we decided to extend the list with more tips and best practices.
Mar 7 2025
How to create a synthetic annotator? The process of developing a domain-specific LLM-as-a-Judge.
In this blogpost we want to introduce the topic of using a Large Language Model (LLM) as an evaluator — a novel approach to tackling the complexities of evaluating advanced machine learning systems, particularly in tasks like Automatic Summarization, Text Generation, and Machine Translation, where traditional metrics struggle to capture nuances like cross-lingual accuracy and bias detection.
Feb 6 2025
The AI dual-use dilemma using the example of China
This article discusses the dual-use dilemma of AI, focusing on China’s approach and the challenges of balancing innovation with security risks, particularly the blurred lines between civilian and military applications.
Dec 20 2024
How we saved over 60% of k8s resources in our frontend platform
In this article, we want to share our journey of searching for optimizations in one of Allegro’s main microservices: opbox-web. You’ll read about the issues we had to deal with and how we managed to overcome them — together with a few surprises along the way and even one golden rule broken.
Dec 19 2024
Automating Periodic Data Transfer from an Operational Database to a Data Warehouse
Many companies face the challenge of efficiently processing large datasets for analytics. Using an operational database for such purposes can lead to performance issues or, in extreme cases, system failures. This highlights the need to transfer data from operational databases to data warehouses. This approach allows heavy analytical queries without overburdening transactional systems and supports shorter retention periods in production databases.
Dec 11 2024
Circuit Breaker not only for HTTP calls! (based on resilience4j)
When we think about the Circuit Breaker pattern, we instantly associate it with the HTTP client. Just make some annotation or wrapper and proceed with coding. In this article, I will encourage you to use this pattern to resolve business problems. Based on a live example from Allegro I will show you how to use the implementation of CircuitBreaker from Resilience4j library for cases other than HTTP calls.
Nov 20 2024
Popular Gradle mistakes (and how to avoid them)
As part of Allegro Hacktoberfest celebrations, Andamio Task Force (the team responsible for Andamio, a set of common libraries used by most JVM projects at Allegro) posted the following message on our social platform…
Oct 7 2024
Do repeat yourself! What is responsibility in code?
Did you know that in October this year, DRY principle will celebrate its 25th anniversary? It was proposed by Andrew Hunt and David Thomas in The Pragmatic Programmer book in 1999. 25th birthday is quite a good reason to celebrate, isn’t it? At least, it’s a good opportunity to bring this principle back into the spotlight and to discuss how to use it properly.
Sep 10 2024
Automating Code Migrations at Scale
At Allegro, we continuously improve our development processes to maintain high code quality and efficiency standards. One of the significant challenges we encounter is managing code migrations at scale, especially with breaking changes in our internal libraries or workflows. Manual code migration is a severe burden, with over 2000 services (and their repositories). We need to introduce some kind of code migration management.
Sep 4 2024
Accelerate test execution in Groovy and Spock
In one of our core services, the execution of a single unit test took approximately 30 seconds, while a single integration test ranged between 65 and 70 seconds. Running the entire test suite took circa 6 minutes.
Aug 26 2024
How to get back to programming after a more than 1.5 year gap - subjective thoughts and tips
Hi, I am Magda and I will tell you a story about coming back to work after a break of 21 months and 2 days. Everything here will be a subjective perspective about my experience.
Aug 5 2024
Migrating Selenium to Playwright in Java - evolution, not revolution
Are you, as a test automation engineer, tired of Selenium’s flakiness? Are you seeking a better tool to automate your end-to-end tests? Have you heard of Playwright? Perhaps you’ve encountered opinions that it is only worth using within a Node.js environment. I have. And as a tester, I decided to verify if this is true. If you’re interested in the results, I encourage you to read the following article.
Jul 26 2024
The noisy JIT Compiler
This article is a case study of how we improved stability in our critical application. It’s mostly a technical analysis of what happens in fresh Java based instance, how JIT Compiler toyed with us at application start and how we learned to control it.
Jul 16 2024
BPMN: The Key to Understanding Business Processes
If you have experience with Event Storming and have ever found yourself wishing there was a way to document the insights gathered during a session, or wanting to communicate the process to other team members, then I have a solution for you. This idea can be expressed in a famous saying: One picture is worth more than a thousand words.
Jul 1 2024
INP — what is the new Core Web Vitals metric and how do we work with it at Allegro.
Site performance is very important, first of all, from the perspective of users, who expect a good experience when visiting the site. The user should not wait too long for the page to load. We all know how annoying it can be when we want to press an element and it jumps to another place on the page or when we click on a button and then nothing happens for a very long time. The state of a site’s performance in these aspects is measured by Web Vitals performance metrics and most importantly by a set of three major Core Web Vitals metrics (LCP — Largest Contentful Paint, CLS — Cumulative Layout Shift, INP — Interaction to Next Paint). They are responsible for measuring the 3 things: loading time, visual stability and interactivity. These metrics are also important for the websites themselves because, in addition to the user experience, they are also taken into account in terms of the website’s positioning in search engines (SEO), which is crucial for most websites on the Internet, Allegro included.
Jun 20 2024
A Mission to Cost-Effectiveness: Reducing the cost of a single Google Cloud Dataflow Pipeline by Over 60%
In this article we’ll present methods for efficiently optimizing physical resources and fine-tuning the configuration of a Google Cloud Platform (GCP) Dataflow pipeline in order to achieve cost reductions. Optimization will be presented as a real-life scenario, which will be performed in stages.
Jun 11 2024
Engineering culture of Allegro & Allegro Pay: Pragmatic Engineer Score
One tech blog/newsletter gained traction and popularity for a couple of years now: Pragmatic Engineer.
Jun 4 2024
REST service client: design, testing, monitoring
The purpose of this article is to present how to design, test, and monitor a REST service client. The article includes a repository with clients written in Kotlin using various technologies such as WebClient, RestClient, Ktor Client, Retrofit. It demonstrates how to send and retrieve data from an external service, add a cache layer, and parse the received response into domain objects.
May 16 2024
Unveiling bottlenecks of couchbase sub-documents operations
This story shows our journey in addressing a platform stability issue related to autoscaling, which, paradoxically, added some additional overhead instead of reducing the load. A pivotal part of this narrative is how we used Couchbase — a distributed NoSQL database. If you find yourself intrigued by another enigmatic story involving Couchbase, don’t miss my blog post on tuning expired doc settings.
Apr 12 2024
Ten Years and Counting: My Affair with Microservices
In early 2024, I hit ten years at Allegro, which also happens to be how long I’ve been working with microservices. This timespan also roughly corresponds to how long the company as a whole has been using them, so I think it’s a good time to outline the story of project Rubicon: a very ambitious gamble which completely changed how we work and what our software is like. The idea probably seemed rather extreme at the time, yet I am certain that without this change, Allegro would not be where it is today, or perhaps would not be there at all.
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