Apr 1 2020
Machine Learning + Agile Manifesto = ?
This post was published on April 1st, 2020, and should not be taken too seriously.
Mar 30 2020
Understanding accessibility
The group that you could help is huge. The Polish Association of the Blind reports that there are more than 3 million people in Poland with visual impairment and 42 thousand with complete blindness (based on official, national statistical data of 2016 - not so fresh; still, it is not better in 2020, so…). These numbers do not include people with other problems, for example, those resulting from severe sickness, with movement disabilities, or with learning problems, older or just foreigners, who are not fluent with the language. All of them, and many more, are not able to use digital products the way people without disabilities do.
Mar 12 2020
Using dotnet new templates to streamline microservices development
You may not know this, but there is a part of Allegro codebase which we started developing in C# due to some special requirements. This implies new programming opportunities and challenges — one of these is creating a completely new .NET Core starter project. Let’s explore one potential solution: dotnet new templates.
Feb 10 2020
Making Webflux code readable with Kotlin coroutines
Recently, our crucial microservice delivering listing data switched to Spring WebFlux. A non-blocking approach gave us the possibility to reduce the number of server worker threads compared to Spring WebMvc. The reactive approach helped us to effectively build a scalable solution. Also, we entered the world of functional programming where code becomes declarative: statements reduced to the minimum immutable data preferred no side effects quite a neat chaining of method calls causing it easier to understand.
Jan 27 2020
How to manage Spring Boot services configuration on GCP
Configuration management is one of the key challenges you have to face when you decide to build an application as a distributed system based on microservices deployed to the Cloud. There are multiple ways of addressing different aspects of this problem, using several tools such as Spring Cloud Config Server or Hashicorp Consul. However, this article will focus on the tools that Google Cloud Platform offers out of the box. The approaches mentioned should be seen as complementary rather than mutually exclusive.
Jan 7 2020
Design for failure - multiple layers of processing to protect against failures.
When designing the architecture of a system, one always needs to think about what can go wrong and what kind of failures can occur in the system. This kind of problem analysis is especially hard in distributed systems. Failure is inevitable and the best we can do is to prepare for it.
Dec 19 2019
Allegro Tech Meeting 2019 — the 12th edition
Surprisingly, this is the first time we share with you a report from Allegro Tech Meeting (ATM) — even though it’s already the 12th edition of this special event.
Dec 12 2019
Grouping and organizing Java classes
One of the first challenges a programmer has to face is organizing classes within a project. This problem may look trivial but it’s not. Still, it’s worth spending enough time to do it right. I’ll show you why this aspect of software development is crucial by designing a sample project’s architecture.
Nov 19 2019
Team tourism at Allegro — part 3 — more case studies
In this last instalment of our series about team tourism at Allegro, our two engineers describe their eventful visits in two rather technical teams, one dealing with our message broker - Hermes, the other with web performance.
Nov 8 2019
Performance of JavaScript optional chaining
One of the coolest features added in just announced TypeScript 3.7 is optional chaining syntax. It promises a much shorter and more readable code for dealing with deeply nested data structures. How may this nice new feature affect the performance of your project?
Oct 14 2019
Team tourism at Allegro — part 2 — case studies
Following up on our previous post about team tourism at Allegro, as promised we present you with three case studies describing experiences of our engineers during their visits in other teams. The teams visited worked on content automation, machine learning and search engine optimisation.
Oct 3 2019
Share what you (don’t) know — how to accelerate your career in IT before it even started
Are you dreaming about getting a job in IT, but you feel stuck? You may be constantly working your way through books and tutorials about the technology that excites you (be it JavaScript, PHP or whatever else), but it still feels like you will never be able to get that Junior Developer position you want.
Sep 16 2019
Team tourism at Allegro
We often hear about the importance of exchanging knowledge and practices between different teams. However, less often do we hear concrete suggestions for how to do it. In this article, we discuss one of our practices to address the problem.
Sep 2 2019
Page visibility and performance metrics
When we measure the page loading speed from the user’s perspective, we pay attention to the appearance of subsequent elements on the screen. Metrics such as First Contentful Paint, First Meaningful Paint and Visually Complete directly reflect what the user sees and when. But what if the page is invisible, when it loads in the background, for example in a different tab? Should we consider such views interesting for us? Don’t the collected metrics distort the results?
Aug 1 2019
A/B testing good practice – calculating the required sample size
Developing our own A/B testing platform from scratch came with many lessons during the process. Our platform was built for people who differ vastly in terms of statistical knowledge, also for those who are not familiar with statistics at all. So the main challenge wasn’t technical implementation. The hardest thing was (and still is) developing good practices and spreading them among our users. We want to share some of our current knowledge that we think is crucial for A/B testing at scale. From this article, you will get to know about calculating sample size, what it means and what benefits it provides for you and your organization.
Jul 15 2019
Migrating a microservice to Spring WebFlux
Reactive programming has been a hot topic on many conference talks for at least several months. It’s effortless to find simple code examples and tutorials and to apply them to greenfield projects. Things become a little bit more complicated when production services with millions of users and thousands of requests per second need to be migrated from existing solutions. In this article, I would like to discuss migration strategy from Spring Web MVC to Spring WebFlux by the example of one of the Allegro microservices. I’m going to show some common pitfalls as well as how performance metrics in production were affected by migration.
Jun 17 2019
Allegro culture — Tech Leaders’ Meeting 2019
How many team leaders do you think there are at Allegro? Earlier this year, about a hundred of us had the chance to meet in person for two days. We tackled company-wide technical challenges, exchanged experiences and discussed the way we and our teams work. We encourage you to read our story since it offers a glimpse at the inner workings of our company and its culture.
May 16 2019
Hermes 1.0 released
After 5 years of developing and maintaining Hermes, we are very excited to announce that version 1.0 has been released.
Apr 9 2019
Why Allegro Ads chose TypeScript
A modern look and fully mobile-friendly design — this is how we created the new version of ads.allegro.pl. Unfortunately, several hundred tests did not protect us from errors. The last straw was when a simple but very annoying problem appeared in production. We decided to start a revolution. We considered Flow, but ended up adopting TypeScript for Allegro Ads.
Apr 1 2019
[April 1st] From PHP to Java and back again: a retreat from microservices
This post was published on April 1st, 2019, and should not be taken too seriously.
Jan 28 2019
Making friends with legacy code
What kind of builders do you use in your tests? Do you use the old good builders where properties are set by a withProperty method? Or maybe, you use builders that make use of closures? As soon as I joined my team, I found out that there is another approach to test builders, and it embraces maps. It seemed innovative, but after a while, it became annoying legacy code. After one of the debugging sessions, I decided to get rid of it, but the monster fought me back.
Dec 18 2018
Java 11 and beyond at Allegro
Since the beginning of my career as a Java developer, keeping up to date with Java was fairly straightforward. Big releases came every few years, causing a bit of mayhem in tooling, IDEs and job interview questions. However with each release there was a lot of time to adjust and migrate to newer versions. With Java 9 things have changed. The so called new release cadence was announced by Oracle. Instead of releasing a new major version each few years, we will get one every half year. This poses a lot of challenges to companies using Java in production, developers and the community as a whole.
Nov 19 2018
It’s all about naming
We all know that “there are only two hard things in Computer Science: cache invalidation and naming things”. However, we know that writing good tests is hard, too. Does it mean that the author of the famous quote is wrong? Not necessarily! In fact, what are tests? These are descriptions of some concepts. They answer the questions: “what?”, “when?” and “how?”. When writing tests, you are answering these questions by giving names to objects, reasons, and processes. I think writing tests is hard because it is all about naming. I believe you can significantly improve your tests just by focusing on giving them correct names. Let me tell you a story of a pull request I was reviewing some time ago.
Oct 22 2018
Turnilo — let’s change the way people explore Big Data
Two years ago at Allegro we used to have a very typical Big Data technology stack. The architecture was based on a Hadoop cluster and we would query it with plain Hive queries, Spark jobs and Jupyter notebooks. Over those last two years we have transformed it into a more efficient and easy to use OLAP platform.
Oct 1 2018
From Simple to Fast - Custom Solr Document Collapsing
At Allegro we use Solr as our main search engine. Due to the traffic to our search engine being thousands of requests per second and index size on the order of a hundred million documents we need to develop custom optimizations. In this post I will describe the story of our Solr plugin development.
