As Senior Software Engineer at company building messaging platform for healthcare industry I am responsible, including other duties, for performance of our application. We develop pretty standard web-service using Ruby on Rails application for business logic and API, React + Redux for users' facing single page application, as database we use PostgreSQL. Common reasons for performance problems in similar stacks are heavy queries to database and I would like to tell the story how we applied non-standard but fairly simple optimisations to improve performance.
Our business operates in US, so we have to be HIPAA compliant and follow certain security policies, security audit is something that we are always prepared for. To reduce risks and costs we rely on a special cloud provider to run our applications and databases, very similar to what Heroku does. On one hand it allows us to focus on building our platform but on the other hand it adds an additional limitation to our infrastructure. Talking shortly — we cannot scale up infinitely. As a successful startup we double number of users every few month and one day our monitoring told us that we were exceeding disk IO quota on the database server. Underlying AWS started throttling which was resulting in a significant performance degradation. Ruby application was not capable to serve all incoming traffic because Unicorn workers were spending too much time awaiting for database's response, customers were unhappy.
I guess almost any programmer who uses .NET will now say this pattern is a piece of cake. That it is the best-known pattern used on the platform. However, even the simplest and well-known problem domain will have secret areas which you have never looked at. So, let’s describe the whole thing from the beginning for the first-timers and all the rest (so that each of you could remember the basics). Don’t skip these paragraphs — I am watching you!
If I ask what is IDisposable, you will surely say that it is
public interface IDisposable
{
void Dispose();
}What is the purpose of the interface? I mean, why do we need to clear up memory at all if we have a smart Garbage Collector that clears the memory instead of us, so we even don’t have to think about it. However, there are some small details.
This chapter was translated from Russian jointly by author and by professional translators. You can help us with translation from Russian or English into any other language, primarily into Chinese or German.
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Three years ago we announced the second publicly available major version of the framework. CUBA 6 was the game-changing version — the licensing was turned from proprietary to Apache 2.0. Those days we couldn't even guess where it was going to bring the framework in long term. CUBA community started to grow exponentially, so we have learned a lot of possible (and sometimes impossible) ways of how developers use the framework. Now we are happy to announce CUBA 7, which, we hope, will make development more coherent and joyful for all community members from those just starting their journey in CUBA and Java to skilled enterprise developers and Java experts.
Some of the numbers that we manage at Kiwi.com include 90 000 000+ daily searches, 25 000 seats sold daily, and a total of 15 000 000 000+ flight combinations available.
Starting from .NET Core 2.0 and .NET Framework 4.5 we can use new data types: Span and Memory. To use them, you just need to install the System.Memory nuget package:
PM> Install-Package System.MemoryThese data types are notable because the CLR team has done a great job to implement their special support inside the code of .NET Core 2.1+ JIT compiler by embedding these data types right into the core. What kind of data types are these and why are they worth a whole chapter?
If we talk about problems that made these types appear, I should name three of them. The first one is unmanaged code.
Both the language and the platform have existed for many years along with means to work with unmanaged code. So, why release another API to work with unmanaged code if the former basically existed for many years? To answer this question, we should understand what we lacked before.
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In 2013, while working at GFRANQ photo service, I participated in the development of an eponymous web service for publishing and processing photos. Filters and transformations were defined in the file with parameters, and all processing was carried out on the server. During service development, there was a need to support these transformations on the client side for the preview. According to Larry Wall, one of the virtues of a programmer is laziness. Therefore, as truly lazy programmers, we thought about the possibility of using the same code on both the server and client sides. The entire development was conducted in C#. After researching the libraries and a couple of attempts, we proudly concluded that this was possible and began to write the universal code.
Why is this article needed? Indeed, 6 years have passed since 2013, and many technologies have lost their relevance, for example, Script#. On the other hand, new ones have appeared. For example, Bridge.NET or Blazor based on the fancy WebAssembly.
Nevertheless, some ideas can still be used. In this article I tried to describe them as detailed as possible. I hope that the mention of Silverlight and Flash will cause a smile with a hint of nostalgia, and not a desire to criticize the old solutions. Anyway, they have contributed to the development of the web industry.
Here is a bit refreshed translation of my 2015 blog post. The post shows how to organize a personal academic library of unlimited size for free. This is a funny case of a self written manual which I came back to multiple times myself and many many more times referred my friends to it, even non-Russian speakers who had to use Google Translator and infer the rest from screenshots. Finally, I decided to translate it adding some basic information on how to use Zotero with rmarkdown.
Bibliographic manager is a life saver in everyday academic life. I suffer almost physical pain just thinking about colleagues who for some reason never started using one — all those excel spreadsheets with favorite citations, messy folders with PDFs, constant hours lost for the joy-killing task of manual reference list formatting. Once you start using a reference manager this all becomes a happily forgotten nightmare.
Now user visits the page and checks out the effect. It’s cool and pleasant small feature, it catches, then user discusses it with colleagues or friends and even repeats the feature. It could be this easy, if not: 
