Nov 10 2022

Vanilla JS is not dead! Microfrontends without web performance issues.

Building a complex web platform can be a real challenge, especially when parts of it are delivered by independent teams. Picking out the correct architecture is crucial, but maintaining it can be even more challenging. Frontend microservices, aka microfrontends, is an architecture that gives a lot of flexibility, but can cause performance issues in the future, if not managed well. This article presents an approach to the microfrontends architecture to keep the frontend technology stack efficient based on the complexity of user interface.


Oct 4 2022

Probabilistic Data Structures and Algorithms in NoSQL databases

What would you say if we stored 1 000 records in a database, and the database claimed that there were only 998 of them? Or, if we created a database storing sets of values and in some cases the database would claim that some element was in that set, while in fact it was not? It definitely must be a bug, right? It turns out such behavior is not necessarily an error, as long as we use a database that implements probabilistic algorithms and data structures. In this post we will learn about two probability-based techniques, perform some experiments and consider when it is worth using a database that lies to us a bit.


Sep 26 2022

Example of modularization in Allegro Pay Android application

Currently, in the Android world, the topic of modularization is very popular. Many bloggers describe their experiences with it and analyze what Google recommends. Our team started the modularization process before it was hot. I will describe our reasons, decisions, problems and give you some advice. We will see if modularization makes sense and what it brings to the table. I will also post some statistics showing what it looked like before and after the modularization process.


Sep 13 2022

How to efficiently write millions of records in the cloud and not go bankrupt — an Azure CosmosDB case study

Cloud providers like to brag about high availability and unlimited scaling of their services – and they are correct, as these features are indeed significant advantages of cloud solutions. Their computational power is so high that for most use cases, it’s almost unlimited. In this blog post, I would like to tell you about our experiences with Azure Cosmos DB and batch processing.


Aug 3 2022

MBox: server-driven UI for mobile apps

In this article, we want to share our approach to using server-driven UI in native mobile apps. In 2019 we created the first version of the in-house server-driven rendering tool called MBox and used it to render the homepage in the Allegro app on Android and iOS. We have come a long way since then, and now we use this tool to render more and more screens in the Allegro apps. After almost three years of working on MBox, we want to share how it works and the key advantages and challenges of using this approach.



Jun 30 2022

GC, hands off my data!

Each of us has probably experienced a time in our career when we wanted to get rid of the Garbage Collector from our application because it was running too long, too often, and perhaps even led to temporary system freezes. What if we could still benefit from the GC, but in special cases, also be able to store data beyond its control? We could still take advantage of its convenience and, at the same time, be able to easily get rid of long GC pauses. It turns out that it is possible. In this article, we will look at whether and when it is worth storing data beyond the reach of the Garbage Collector’s greedy hands.



Jun 7 2022

How to include refactoring into product development roadmap? Reducing technical debt inspired by real options identification

Nowadays, technical debt can be considered the bread and butter of most IT-powered enterprises around the world. Almost every company that survived the startup phase and managed to deliver its first products to customers will face at some point technical challenges related to past architectural decisions. Although code engineering gets better every year, we cannot argue with the obvious fact of life: the market will always force many of us to deliver tech products faster than we wish. Time To Market has always been a key success factor for many product companies and it puts a lot of pressure on Engineering to keep up with challenging deadlines.




Mar 30 2022

Visual thinking

We use written (source code) language to express our intentions in a machine-readable form. We use spoken language to communicate with other people. We pride ourselves as ones choosing a programming language optimized to the task at hand. Do we use the optimal way to express our ideas?



Mar 1 2022

The War in Ukraine

The attack on Ukraine has shocked the entire world, but in Poland it is making especially big waves. Not just due to geographical proximity - Ukrainians are one of the largest minorities in Poland and simply put it is affecting people we know personally.



Feb 10 2022

Why should we rewrite enzyme.js to react-testing-library and how to do that?

Everyone repeats like a mantra that tests are an indispensable element of development work. Is there anything to it? Well, I need to admit that as a developer, I rather often want to skip the test writing stage. I assume I’m not the only one. I’m aware that it’s a mistake, even with testers on board. Effective and efficient testing of your own code can help with catching bugs in new functionalities, as well as in changes to already existing ones. It cannot be questioned. Sometimes tests also help to understand how some long-unused functionality or component works. And that’s a small bonus too. Can a large project cope without testing? Probably so. But the number of errors and their severity will probably be much higher. That’s why in Allegro Ads we pay attention to writing tests.


Jan 24 2022

How do coroutines work internally in Python?

Most of applications we create are basically loops. An average program waits for an event, then processes it following some business logic. Afterwards it begins waiting for another event to arrive. Java Servlets work this way too. Popular frameworks such as Spring allow us to only care about the business logic, while the framework takes care of the application main loop.


Jan 12 2022

Shrinking the size of a monorepo

The source code of Allegro iOS app for buyers used to be divided into separate modules hosted in multiple repositories (polyrepo). The source code was migrated to a monorepo a few years back along with the history of all repos that constituted the app. Updating source code of a module on one repository could affect another module hosted on a separate repository. Versioning modules and propagation of dependency update led to long release process of the entire application. Our main repository for the iOS application thus became our monorepo. After 9 years of development of the app the repo size has grown enormously and the git clone command became a nightmare taking too much time. We had a possibility to shrink the project size during the migration from an on-premise to an external git repo hosting provider.



Dec 13 2021

Clean Architecture Story

The Clean Architecture concept has been around for some time and keeps surfacing in one place or another, yet it is not widely adopted. In this post I would like to introduce this topic in a less conventional way: starting with customer’s needs and going through various stages to present a solution that is clean enough to satisfy concepts from the aforementioned blog (or the book with the same name).


Dec 9 2021

Which skills to choose in order to be more valuable

At some point in your career, you realize that it’s time to try to advance through the hierarchy. You think you are doing a good job. You are constantly developing and learning something new. But at the same time, someone you know, with much less experience and knowledge than you, has long been higher up the hierarchy than you. Then you ask yourself: what is wrong with me? In my case, the answer turned out to be properly gathering the expectations concerning my skills and work.


Nov 22 2021

Moving towards Micronaut

Micronaut is one of the new application frameworks that have recently sprung up. It promises low memory usage and faster application startup. At Allegro we decided to give it a try. In this article we’ll learn what came out of it and if it’s worth considering when creating microservices-based systems.


Nov 9 2021

OAuth rate-limiting

Every e-commerce platform needs some kind of central authorization system. At Allegro we use OAuth and have our own implementation that stays true to the RFC. Allegro has millions of users. There are also a lot of requests that go through OAuth services. At some point there comes a need to have better control over how much traffic we want to allow in a certain time window, while maintaining full performance of the platform. Here is where the idea of rate-limiting comes in handy.


Oct 26 2021

How we refactored the search form UI component

This article describes a classic case of refactoring a search form UI component, a critical part of every e-commerce platform. In it I’ll explain the precursor of change, analysis process, as well as aspects to pay attention to and principles to apply while designing a new solution. If you are planning to conduct refactoring of a codebase or just curious to learn more about frontend internals at Allegro, you might learn a thing or two from this article. Sounds interesting? Hop on!

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