Jan 14 2021
So I was tuning one of our services in order to speed up some MongoDB queries. Incidentally, my attention was caught by
the size of one of the collections that contains archived objects and therefore is rarely used. Unfortunately I wasn’t
able to reduce the size of the documents stored there, but I started to wonder: is it possible to store the same data
in a more compact way? Mongo stores JSON that allows many different ways of expressing similar data, so there seems
to be room for improvements.
Dec 28 2020
Programmers who have ever developed software for Apple platforms in the early days of Swift language might remember ridiculous
times it took to compile the whole project. For large and complicated codebase times used to range from 10 up to 40 minutes.
Over the years our toolset has improved alongside with compilation times, but slow build times of source code can still be a nightmare.
Dec 17 2020
When we developed our Allegro iOS app adding new features and with more people contributing to the codebase, we noticed
that build times began to grow. In order to have precise metrics, we started to track clean build time as well as the
amount of code we had. Do these two metrics grow at the same pace?
Dec 7 2020
Marketing is a very important department in every company. In case of Allegro,
marketing is especially difficult because you have so many products to promote.
In this post we will tell the story of a platform we built for marketing
purposes.
Nov 23 2020
JavaScript Frameworks play an important role in creating modern web applications.
They provide developers with a variety of proven and well-tested solutions for creating efficient and scalable applications.
Nowadays, it’s hard to find a company that builds its frontend products without using any framework,
so knowing at least one of them is a necessary skill for every frontend developer.
To truly know a framework, we need to understand not only how to create applications using it, but also how to test them.
Nov 4 2020
We are excited to announce that we have just released BigFlow 1.0 as open source.
It’s a Python framework for big data processing on the Google Cloud Platform.
Oct 15 2020
Imagine that you were charged with finishing a task started by your colleague. He or she implemented it just before leaving for a vacation. Now it is your job to finish and release it.
Oct 1 2020
Most applications need to be able to persist and retrieve their state to be fully functional.
In my previous post I compared methods for persisting application state.
In this post I will compare the methods for retrieving this state.
Sep 3 2020
Every day, many developers of enterprise systems have to face complex problems for which incorrect solutions often end with a loss of enormous amounts of money.
That’s why they constantly learn new paradigms, frameworks, tools, read books and broaden their knowledge in technical conferences.
It’s a lot of time and effort! All this dedication is on behalf of creating a high-quality product — but what is the result?
Obviously it depends (as every software architect would say), but too many times the result isn’t the best.
It takes a while, has got too many errors, often the code quality isn’t high…
And let’s better not mention testing. Why is all this happening then?
Everyone does their best, spends additional time on learning, so what exactly is missing?
The answer is quite straightforward - constant practicing.
Let’s say a few words about “code kata” which can make a remedy for the mentioned problems.
Aug 11 2020
Let me start with a story. Once upon a time I stumbled upon an excellent
article by Philip Walton where he describes how expensive
script evaluations could (and should!) be deferred until the browser is idle or they are actually needed. One of the
examples that awakened my interest was creating an instance of the Intl.DateTimeFormat object, as I was using this
great API quite often but never thought it can cause real performance problems. Turns out it can, especially if
used inside loops. Apart from the technique
described in Philip’s article, another solution is to simply reuse Intl.DateTimeFormat instances instead of creating
them every time.
Jul 16 2020
We run over 800 microservices in our on-premise and public clouds. They are developed by hundreds of engineers
in various technologies: from the most popular Java and Kotlin, through Scala, Clojure, Python, NodeJS, Golang, to
less mainstream like Elixir or Swift. All these applications need to handle common
technical concerns: logging, monitoring, service discovery, tracing, internationalization, security and more.
How to provide common solutions to these requirements in such a heterogeneous setup?
In this post I’m going to explain how we originally solved this problem with common libraries
and how we are currently changing our runtime environment to make things even easier.
Jun 22 2020
An application can be defined as a set of use cases.
It often happens that use case A requires a previously executed use case B for its execution.
In such situation, it should be ensured that use case B has been executed while executing use case A.
To achieve this, application state that is common to both use cases, is introduced.
The state must be persisted to be visible to more than one use case.
Most often, various types of databases are used for this purpose.
While working with source code, I have encountered various methods of persisting the application state.
I also came up with my own variations.
In this post I will make a subjective comparison of these methods based on specific criteria.
May 21 2020
When you go through articles related to Hexagonal Architecture (HA) you usually search for practical examples.
HA isn’t simple, that’s why most trivial examples make readers even more confused, though it is not as complex as many
theoretical elucidations present it. In most posts you have to scroll through exact citations or rephrased definitions of concepts such as
Ports and Adapters or their conceptual diagrams. They have already been well defined and described by popular authors i.e.
Alistair Cockburn or Martin Fowler.
I assume you already have a general understanding of Domain Driven Design and that you understand terms such as Ports and Adapters.
I’m not a HA expert, yet I use it everyday and I find it useful. The only reason I write this post is to show you that Hexagonal Architecture makes sense, at least if your service is a little more than a JsonToDatabaseMapper.
May 7 2020
This year Allegro.pl turns 21. The company, while serving millions of Poles in their
online shopping, has taken part in many technological advances. Breaking the monolith,
utilising public cloud offerings, machine learning, you name it. Even though many technologies
we use might seem as just following the hype, their adoption is backed by solid reasoning.
Let me tell you the story of a project I’ve had the privilege of working on.
Apr 16 2020
As a developer interested in both web technologies and game development I always found myself
disagreeing with a large part of articles about using a particular technology to solve some problems.
While such articles are often true, they often skip some important details that make given
solution unacceptable in some other cases. And in this article I will try to look at
immutability in a negative way from game development perspective and how it can affect web services too.
It is always more fun to look in a negative way at something everyone loves ;)
Apr 1 2020
This post was published on April 1st, 2020, and should not be taken too seriously.
Mar 30 2020
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
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
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
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
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
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
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
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
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?
