Jan 12 2022
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 20 2021
A new version of MongoDB, 5.0, has been recently launched. The list of changes included one that I found particularly interesting: the time series collections. It is a method of effective storing and processing of time-ordered value series. In this article we will verify whether the processing of time series is really as fast as promised by the authors.
Dec 13 2021
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
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
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
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
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!
Oct 18 2021
One of the key elements ensuring efficient operation of the services we work on every day at
Allegro is fast responses from the database.
We spend a lot of time to properly model the data so that storing and querying take as little time as possible.
You can read more about why good schema design is important in one of my earlier
posts.
It’s also equally important to make sure that all queries are covered with indexes of the correct type whenever
possible. Indexes are used to quickly search the database and under certain conditions even allow results to be
returned directly from the index, without the need to access the data itself. However, indexes are not
all the same and it’s important to learn more about their different types in order to make the right choices later on.
Oct 7 2021
It’s easy to find resources about improving Elasticsearch performance, but what if you wanted to reduce it?
In Part I of this two-part series we looked under the hood in order to learn how
ES works internally. Now, in Part II, is the time to apply this knowledge in practice and ruin our ES performance. Most tips should also be applicable to
Solr, raw Lucene, or, for that matter, to any other full-text search engine as well.
Sep 30 2021
It’s easy to find resources about improving Elasticsearch performance, but what if you wanted to reduce it?
This is Part I of a two-post series, and will present some ES internals. In Part II
we’ll deduce from them a collection of select tips which can help you ruin your ES performance in no time. Most should also be applicable to
Solr, raw Lucene, or, for that matter, to any other full-text search engine as well.
Sep 23 2021
The main goal of boosting website performance is to improve the user experience. In theory,
a satisfied customer is more likely to use a particular company’s services, which is then reflected in business results.
However, from my own experience I can say that not every change can be easily converted into money.
I would like to tell you how to reconcile these two worlds, how to convince the business that the benefits of
better performance are a long-term investment, and how to streamline the development process during the design or code writing process.
Sep 6 2021
Imagine you have to migrate your JavaScript project to TypeScript. It’s fairly simple to convert one file from JS to TS, but if
you want to take type checking to the next level (going for TypeScript’s strict mode) it is not that easy. The only solution you
have is turning on strict mode for the whole project which may result in thousands of errors. For most projects that are not strict yet,
it would take quite a bit of time and effort to fix all the strict errors at once.
Aug 10 2021
The following article is an excerpt from Software Mistakes and Trade-offs book.
In real-world big data applications, the amount of data that we need to store and process can be often counted in the hundreds of terabytes or petabytes. It is not feasible to store such an amount of data on one physical node. We need a way to split that data into N data nodes.
Jul 29 2021
It’s been over 5 years since the introduction of the article describing the ongoing transformation of Allegro’s frontend architecture — an approach that was later formalized by the industry under the name of Micro Frontends. I think that after all this time we can safely say that this direction was correct and remained almost entirely unchanged in relation to the original idea. Still, some of the challenges foreseen in the publication soon became the reality. In this article I would like to focus on the CSS part of the whole adventure to tell you about how we manage consistency and frontend performance across over half a thousand components, and what it took us to get to where we stand today.
Jul 21 2021
Almost every modern web application somehow interacts with a backend - be it loading data, doing background sync, submitting a form, or publishing the metrics.
Making API requests is not an easy task - we have to consider multiple outcomes and handle them properly. Otherwise, we might end up with confused users and
decreased conversion. Although the stakes are high, it is still very likely to encounter an application designed with only a happy path scenario in
mind. The question is - how can we improve it?
Jun 28 2021
Some time ago, our team faced the issue of moving an existing Apache Spark job from an on-premise Hadoop cluster to public cloud.
While working on the transition we came across another way to process data that is Apache Beam. We were curious whether this tool had
more advantages in comparison to traditional Apache Spark. We wanted to find the answer relatively quickly with minimal effort. Hence, we built two projects to
process the same data using these technologies. Below you can get to know the architecture of the jobs written in Apache Spark and Apache Beam.
Jun 17 2021
I’m a big fan of logging as much extra data as possible. I’m also a DRY approach believer. I feel strong anxiety when I see repetition in code.
Combining all these “passions” is not always easy. It’s hard to log everything without repeating things. Even if it’s possible, it usually leads to inelegant code.
Jun 8 2021
Some time ago we announced that Allegro passes Core Web Vitals assessment and thanks to that we were awarded in “Core Web Vitals Hall of Fame”.
It means that Allegro is in the group of the 27% fastest websites in Polish Internet.
May 21 2021
Accurate forecasting is key for any successful business. It allows one to set realistic financial goals for the next quarters, evaluate impact of business decisions, and prepare adequate resources for what is coming.
May 11 2021
The beginnings in a new job can be really tough, especially in such uncertain times as the pandemic. Remote onboarding, Zoom meetings, inability to talk
face-to-face — it’s a big test, especially if you’re switching industries. My story is quite similar: in July 2020 I started a three-month internship at Allegro
to train for product management. When the internship ended, I was offered to stay permanently as Junior Product Manager. I’d like to describe my beginnings at
Allegro. But first — a few words about me.
Apr 13 2021
According to Wikipedia there are approximately 700 computer languages available. Seven hundred.
This is an unbelievable number and it’s the reason why programmers face the problem of
choosing a programming language to work with, which frameworks to use and which tech stack to learn.
All of them have pros and cons, but when looking for an all-purpose language you should take Kotlin
into consideration and ask yourself the question: “Do I really need another programming language?”.
Mar 23 2021
Maybe it’s another “How I’ve changed my worklife” story, but I hope it is an interesting one. It seems quite important to tell: before the beginning of my
Allegro adventure, I was working as… an archaeologist. It was both physical work on excavations and research work at my PhD studies. And the only thing that
connects my past work and the current one is: attention to detail.
Mar 5 2021
Coordinating complex processes, both business and technical, can be a challenging issue in a distributed system.
Especially when the complications associated with them, such as concurrency, idempotency, scalability and hindered
testability, come into play — possibly all at once.
This is definitely something that can keep many programmers awake at night.
Feb 15 2021
So you’re new to Allegro, have just finished your tech onboarding and are stunned with information overflow? Or perhaps you
are planning to join Allegro and don’t know what it looks like in here? I am about to try and describe how I felt just a few months ago and what startled or
dismayed me. I hope this short article will answer all your concerns.
Feb 1 2021
Many of us spend most of their software development careers improving and extending applications protected by pre-existing security mechanisms. That’s why
we rarely address problems related directly to authentication and authorization unless we build apps from scratch.
Regardless of your experience I still hope you will find this article interesting.
It’s not meant to be a tutorial. I would like to focus on clarifying basic concepts and highlighting common misconceptions.
