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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Optimizing and Improvement a Web Application Using Open Source Tools</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Yuri Kravchenko</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Olga Leshchenko</string-name>
          <email>olga.leshchenko@knu.ua</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Oleksandr Trush</string-name>
          <email>oleksandr.trush@knu.ua</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Nataliia Dakhno</string-name>
          <email>nataly.dakhno@ukr.net</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Pavlo Krasnopyorov</string-name>
          <email>pavlokrasnopyorov@knu.ua</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Taras Shevchenko National University of Kyiv</institution>
          ,
          <addr-line>Volodymyrs'ka str. 60, Kyiv, 01033</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <fpage>368</fpage>
      <lpage>379</lpage>
      <abstract>
        <p>This paper analyzes the optimization of a web application using modern open source tools such as Lighthouse and K6. The main goal was to improve the quality and productivity of the additive. The study finally analyzed important metrics such as number of HTTP requests, duration of HTTP requests, HTTP request waits, HTTP requests per second, as well as key indicators such as First Contentful Paint, Largest Contentful Paint, Total Blocking Time, cumulative layout shift and speed index. The results of this analysis show significant improvements in all the specified metrics, which undoubtedly emphasizes the effectiveness of the optimization methods and tools used. The number of HTTP requests has increased and their duration has decreased, which degrades the overall speed of processing requests. It is important to note that the page load time has become significantly faster, with a significant reduction in First Contentful Paint and Largest Contentful Paint. These improvements not only enhanced the user experience, but also positioned the app as more competitive in the market.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
    </sec>
    <sec id="sec-2">
      <title>2. Overview of web application optimization methods</title>
      <p>
        There are many options for how to optimize a web application, but to group and systematize them,
you can use the OSI (Open Systems Interconnection) model [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. By looking at the OSI model, we can
identify at which network layer optimization techniques can be applied to improve the performance of
a web application. Application layer, which is the upper level of the OSI model and plays the most
important role in the use of optimization methods. This level includes applications and services that
provide users with multi-functional capabilities. Applying optimization techniques at the application
layer level has great potential to improve performance, efficiency, and user experience.
      </p>
      <p>
        Analyzing web application optimization methods involves using a variety of tools to evaluate and
analyze the effectiveness of different optimization approaches. This includes both
mathematical
methods of optimization [
        <xref ref-type="bibr" rid="ref4 ref5 ref6">4 - 6</xref>
        ] and instrumental methods. These tools help you understand which
optimization techniques are best to use to improve the performance and speed of your web application.
      </p>
      <p>
        One of the main analysis tools is application performance analysis. It includes collecting and
analyzing server load data, user feedback, page load speed, and other performance metrics [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
Information obtained from monitoring helps to identify problem areas and potential optimization areas
[
        <xref ref-type="bibr" rid="ref8 ref9">8, 9</xref>
        ]. App performance analysis involves evaluating various metrics that help determine how well the
app is performing and how its performance affects the user experience [
        <xref ref-type="bibr" rid="ref10 ref11">10, 11</xref>
        ].
      </p>
      <p>Response Time: The average response time can be determined using the mathematical
expectation (average) response time for all requests. The equation can look like this:</p>
      <p>=  Σ ,
where T - is the response time of each individual request, and N - is the quantity of requests.</p>
      <p>Page Load Time: This metric can be calculated as the sum of the loading time of individual
resources (images, CSS, JavaScript, etc.) that are included on the page.
where ResourceLoadTime - is the loading time of each resource.
used relative to the maximum available resources.</p>
      <p>Resource Usage: CPU time and memory usage can be measured as the percentage of resources</p>
      <p>PageLoadTime = ΣResourceLoadTime,
Reliability: It is possible to use the quantity of errors to determine reliability.</p>
      <p>=


=


=


∗ 100%,

∗ 100%,
∗ 100%,</p>
      <p>User Interaction Response Time: Response time to user interaction can be determined by
measuring the time between sending a user request and receiving a response.</p>
      <p>= 
− 
where EndTime - is the time of receiving a response, and StartTime - is the time of sending a request.</p>
      <p>These equations represent general approaches to measuring various performance metrics. Specific
equations and measurement metrics can be adapted depending on the application and measurement
methodology.
2.1.</p>
    </sec>
    <sec id="sec-3">
      <title>Tools for web application performance analysis</title>
      <p>Paragraph text. Paragraph text. Analysis tools play an important role in the process of optimizing
web applications. They provide us with the opportunity to get detailed information about the
performance and efficiency of our application, identify problem areas and find ways to solve them.</p>
      <p>
        First of all, analysis tools allow you to monitor the performance of a web application in real time
[
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]. They provide collection and visualization of key metrics such as server recall time, page load time,
memory usage, and more. This allows you to identify speed issues that may affect the user experience.
      </p>
      <p>Next, analysis tools provide the ability to perform detailed audits of web applications in terms of
loading speed, resource size, caching, and other factors. They help identify problem areas that can be
optimized, such as reducing file size, using caching to reduce server requests, etc.</p>
      <p>In addition, the analysis tools provide the ability to conduct load tests that allow you to simulate
heavy loads on a web application and evaluate its performance and stability. This allows you to identify
problems of scalability, insufficient optimization or instability of the system.</p>
      <p>
        Popular web application analysis and optimization tools include:
1. k6 - is a high-performance tool for load testing and performance verification [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ]. It allows
developers and engineers to test the scaling of web applications and network services and evaluate their
performance under different loads. Benefits: An easy-to-use tool for load testing and performance
verification. Supports JavaScript scripting and provides detailed reports. Disadvantages: Some
advanced features may only be available in the commercial version. Figure 1 shows an example of use.
      </p>
      <p>
        2. GTmetrix: It is an online tool that provides a detailed report on the performance of web pages.
GTmetrix evaluates page load speed, file size, quantity of server requests and other metrics. It also
provides optimization recommendations to improve performance [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ]. Benefits: Provides in-depth
performance analysis, including download speed estimates, image optimization, caching, and other tips.
It has a user-friendly interface and supports many test locations. Disadvantages: Some features are only
available in the paid version. Reports can be a bit complicated for beginners. Figure 2 shows an example
of use.
      </p>
      <p>
        1. WebPageTest: It is a tool that allows you to test the loading speed of web pages from different
locations around the world. It provides detailed information on load hours, page size, server requests,
and other metrics [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ]. WebPageTest also allows you to run repeated tests to monitor hourly
performance. Benefits: Provides detailed performance reports including load speed, page load analysis,
query waterfall and other metrics. Allows you to choose the test location and different configurations.
Disadvantages: The interface may seem difficult for beginners. There are a limited quantity of free
requests. Figure 3 shows an example of use.
      </p>
      <p>
        2. Pingdom: It is a performance monitoring tool that provides information on page load hours, file
sizes, quantity of requests, and other metrics [
        <xref ref-type="bibr" rid="ref16">16</xref>
        ]. He has too the ability to monitor site performance on
an ongoing basis and send notifications about any problems. Pros
      </p>
      <p>3. An easy-to-use tool that provides information about website loading speed and availability. It has
a user-friendly interface and supports many test locations. Disadvantages: Limited functionality
compared to other tools. Some advanced features are only available in the paid version. Figure 4 shows
an example of use.</p>
      <p>
        4. YSlow: This is a browser extension that provides web page performance scores based on Yahoo's
recommendations [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ]. YSlow analyzes various aspects, including caching, file compression, CDN
usage, and more, and provides recommendations for improving performance. Benefits: Analyzes web
page performance, offers optimization tips such as resource compression, caching, and other
improvements. Integrated with Firebug browser extension. Disadvantages: The development of the tool
has been frozen, so it may be less relevant compared to newer tools. Figure 5 shows an example of use.
      </p>
      <p>
        5. Apache JMeter: It is a tool for testing server performance and load. It allows simulation of a
large volume of requests to a web application, which helps to evaluate its performance and identify
problem areas [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ]. Pros: Powerful performance and load testing tool. Supports many protocols and can
simulate different load scenarios. Disadvantages: Requires study and experience to use effectively.
Does not provide a visual report, requires analysis of results. Figure 6 shows an example of use.
      </p>
      <p>
        These tools help you analyze and optimize the performance of your web applications to provide a
better user experience and faster page load times. Thanks to the analysis tools, there is confidence that
the web application is running at optimal performance and provides a fast and convenient user
experience. Considering these factors, Lighthouse [
        <xref ref-type="bibr" rid="ref18 ref19">18, 19</xref>
        ] and k6 were chosen as effective tools for
query testing in a commercial web application. These tools provide ease of use, flexibility in test setup,
analysis of results, and extensibility. Help identify problems, analyze test results, and make informed
decisions about app optimization.
      </p>
    </sec>
    <sec id="sec-4">
      <title>3. Development of a web application</title>
      <p>Web application development includes two main components: client-side and server-side
development. Each of these components has its own unique requirements and tasks that are necessary
for the successful implementation of the project.</p>
      <p>The client part of the web application corresponds to the interaction with the user and the display of
information on his devices. Technologies such as HTML, CSS and JavaScript programming language,
as well as modern frameworks and libraries that simplify the work of creating an interactive interface
are used to develop the client part.</p>
      <p>The server part of the web application is responsible for processing user requests, saving and
retrieving data from databases, as well as for the application's business process logic.</p>
      <p>When developing an optimized web application, the Next.js framework will be used, which is one
of the popular and powerful frameworks for developing React-based web applications. One of the main
advantages of Next.js is that it works both on the client side and on the server side, which makes it an
ideal choice for optimizing applications.</p>
      <p>
        A commercial web application was chosen for the optimization study. Here are some reasons that
explain the choice: increased conversions, large volumes of data, SEO and search ranking [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ].
      </p>
      <p>Choosing a commercial web application allows you to uncover the most possible optimization
methods, after which it requires attention to speed, performance, security, user experience and other
factors that are crucial.</p>
    </sec>
    <sec id="sec-5">
      <title>4. Evaluation of the effectiveness of the web application</title>
      <p>Web application development includes two main components: client-side and server-side
development. Each of these components has its own unique requirements and tasks that are necessary
for the successful implementation of the project.</p>
      <p>
        To evaluate the performance of the web application, we will use Lighthouse, which is an open tool
for analyzing the performance and quality of web applications, as well as K6 to create a stress test.
Lighthouse was developed by the Chrome DevTools team and provides tools for evaluating
performance, accessibility, SEO optimization, and other aspects of a web application [
        <xref ref-type="bibr" rid="ref21 ref22">21, 22</xref>
        ]. The main
function of Lighthouse is to automatically audit a web page using a set of rules and recommendations.
The Lighthouse performance score is a weighted average of metrics, with more weighted metrics having
a greater impact on the overall performance score. Scores of indicators are not displayed in the report,
but are calculated according to the formula shown in Figure 6.
Key performance metrics that can be measured include:
1. First Contentful Paint (FCP): This is the time it takes to display the first content on the page.
It can be text, images or other elements. The smaller the FCP value, the faster the web page will
display the first content. Figure 7 shows how the metric value is interpreted for loading.
The FCP is calculated as the difference between the FCP time and the initial page load time:
 = tFCP −  , (6)
2. Cumulative Layout Shift (CLS): This is a metric that measures how unstable the elements on
the page are when loading. It measures how much the page layout changes on load, which can lead
to an unpleasant user experience, such as when they try to click on an element but it suddenly shifts.
CLS is calculated as the sum of the cumulative displacements of objects on the page during loading.
Each change in the position of the object is taken into account with a weighting factor depending on
the visibility of the object and the size of the page. Mathematically, this can be expressed as:
 =  (  ∗   ∗  ), (7)
where:
 Impact fraction - fraction of displacement caused by a change in the object's position.
 Distance fraction - the fraction of the visible area of the page that was affected by the change
in the object's position.
      </p>
      <p> Distance - the actual distance the object moved.
3. Largest Contentful Paint (LCP): This is the time it takes to display the largest piece of content
on the page. It can be a large image, video or other important element that attracts the user's attention.
Figure 8 shows how the metric value is interpreted for loading.</p>
      <p>The LCP is calculated as the difference between the LCP time and the initial page load time:

= 
− 
,


t_start - the time the page started to load,
t_LCP - the time when the largest content becomes visible.
4. Total Blocking Time (TBT): This is the time when the page is blocked and unavailable for user
interaction due to the execution of JavaScript code. Figure 9 shows how the metric value is
interpreted for loading.</p>
      <p>The mathematical model for TBT can be expressed as follows:
 Blocking Time for each task (such as JavaScript or rendering): The amount of time the page is
blocked during a specific task. Let's denote this time as BT_i, where i is the index of a separate task.
 Quantity of tasks (N): Quantity of all tasks that blocked the page.
 Total Blocking Time, TBT: This is the total block time for all tasks:
Figure 9: Metric LCP
5. Speed Index: This is the time that shows how quickly the content is displayed visually when the
page loads. First, Lighthouse captures a video of the page loading in the browser and calculates the
visual transition between frames, then uses the Speedline Node.js module to calculate the speed index.
Figure 11 shows how the metric value is interpreted for loading.
(8)
(9)</p>
      <p>Taking into account these optimization metrics helps to make an objective assessment of the
performance of the web application. Comparing these metrics to set goals and standards will help
identify issues and make optimizations to improve performance and user experience.</p>
    </sec>
    <sec id="sec-6">
      <title>5. Experimental study of optimization methods using Lighthouse and K6 tools</title>
      <p>
        An experimental study of the optimization of a web application can include several stages, and the
main emphasis will be on using the Lighthouse tool for local testing [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ] and conducting tests in
different regions for hosting on the domain where the web application is located, as well as stress testing
using tools K6 [
        <xref ref-type="bibr" rid="ref24 ref25">24, 25</xref>
        ]. The results of testing in different regions on the main page are in Figure 12 and
Figure 13, respectively.
      </p>
      <p>Performance testing for different regions is an important part of the web application optimization
process. It helps ensure global availability, improve user experience and determine the optimal hosting
settings for the application.</p>
      <p>The K6 tool was chosen for the stress test - it is a very powerful tool for stress testing and loading
web applications and APIs. It is designed to help developers and engineers test the speed and stability
of their systems under heavy load.</p>
      <p>One of the advantages of the K6 is its ease of use. It has a simple syntax that allows you to quickly
create and configure tests. K6 is written in the Go programming language, which makes it fast and
efficient. It also has built-in support for JavaScript, allowing you to use your own code to create
complex test scenarios. The configuration of the script with comments is presented in Figure 14.</p>
      <p>Uses the http module from K6 to make a GET request to a web application URL.</p>
      <p>The Options object contains the K6 configuration parameters. We define different stages (stages)
for the load, increasing it to 100 virtual users for 10 seconds, maintaining it at this level for the next
minute, and then reducing it to 0 for another 10 seconds. The Thresholds object allows you to set
threshold values for metrics. We use http_req_duration (duration of requests) and set the threshold that
95% of requests have a duration of less than 500 ms. The results of the k6 web application before and
after the application of optimization methods are shown in Figures 16 and 17, respectively.</p>
      <p>When using the K6 tool, the following results were obtained:
1. Quantity of HTTP requests. Includes all successful and failed requests. 2603 queries were
executed before optimization, and 20222 queries were received after using the K6 tool. The increase
indicates that the optimization of the application contributed to more efficient processing of requests
and resources, which helps to reduce the load on the server.</p>
      <p>2. HTTP request duration. Before optimization, it was 2.72 seconds, and after using the K6 tool,
312.17ms was obtained. The duration of requests decreased by 88.43% after optimization. The
reduction indicates that the app has become more responsive and responds quickly to user requests,
which improves the overall user experience.</p>
      <p>3. Waiting for HTTP requests. Before optimization, it was 2.72 s, and after using the K6 tool, 312.92
ms was obtained. Expectation decreased by 88.29%. The reduction indicates optimization of the
application's network interaction, which contributes to higher performance and responsiveness.</p>
      <p>4. Quantity of HTTP requests per second. Before optimization, it was 32.46 requests/s, and after
using the K6 tool, 252.76 requests/s were obtained. The 678.6% increase shows the app's ability to
serve more users simultaneously and improves its scalability.</p>
      <p>After carrying out two stress tests for the web application - before optimization and after
optimization, we can draw the following conclusions: performance has improved, loading time has
decreased, resource consumption has decreased, and scalability has improved.</p>
      <p>At the next stage, the Image component and Content Delivery Network (CDN) were used to improve
the speed and performance of web applications. Figure 17 shows the Lighthouse results for a web
application without adding optimization methods, and Figure 18 shows the values of these metrics.</p>
      <p>Figure 19 shows the Lighthouse results for the web application after adding optimization methods,
and Figure 21 shows the values of these metrics
Running the Lighthouse tool produced the following results:
 First Contentful Paint (FCP) reduced by 75%, from 1.2 seconds to 0.3 seconds.
 Largest Contentful Paint (LCP) decreased by 92%, from 12.6 seconds to 1.0 seconds.
 Total Blocking Time (TBT) reduced from 570 milliseconds to 0 milliseconds.

</p>
      <p>Cumulative Layout Shift (CLS) changed slightly, from 0 seconds to 0.004 seconds.</p>
      <p>Speed Index decreased by 95,2%, from 6.3 seconds to 0.3 seconds.</p>
      <p>1. First Contentful Paint (FCP): A decrease of 75% indicates a significant increase in the speed of
displaying the first content on the page, which makes the application more attractive to users.</p>
      <p>2. Largest Contentful Paint (LCP): The 92% reduction shows a dramatic improvement in the load
time of the largest content on the page, which is immediately noticed by users.</p>
      <p>3. Total Blocking Time (TBT): The reduction from 570 milliseconds to 0 milliseconds emphasizes
the absence of blocking operations that can interfere with user interaction.</p>
      <p>4. Cumulative Layout Shift (CLS): A slight change from 0 seconds to 0.004 seconds indicates a
stable page display during loading.</p>
      <p>5. Speed Index: A reduction of 95,2% indicates a significant acceleration of page rendering and
contributes to an excellent user experience.</p>
      <p>After analyzing a baseline web application and an application with recommendations implemented
using Lighthouse, you can compare the resulting metrics and understand how the optimization
techniques improved the performance, availability, compliance with best practices, and SEO of the web
application. The results of the comparison will help identify the strengths and weaknesses of the
application and direct efforts to further optimization and performance improvement.</p>
    </sec>
    <sec id="sec-7">
      <title>6. Conclusions</title>
      <p>As a result of the work carried out, which used modern open-source tools such as Lighthouse and
K6 to optimize the web application based on Next.js, TypeScript, TRPC, Prisma, Postgres and Vercel,
significant improvements in quality and application performance.</p>
      <p>Analysis of the test results with K6 indicates a significant improvement in important metrics such
as the quantity of HTTP requests, the duration of HTTP requests, the waiting time of HTTP requests,
and the quantity of HTTP requests per second. This indicates an effective optimization that reduced the
load on the server and made the application more responsive.</p>
      <p>The results of the Lighthouse analysis are also impressive: reductions in First Contentful Paint,
Largest Contentful Paint, Total Blocking Time, Cumulative Layout Shift and Speed Index indicate a
significant acceleration of loading and displaying page content. This makes the app more attractive to
users and improves their overall experience.</p>
      <p>In summary, the use of optimization methods and performance measurement tools allowed to
improve the quality and speed of the web application, ensuring user satisfaction and increasing its
competitiveness in the market.</p>
    </sec>
    <sec id="sec-8">
      <title>7. References</title>
    </sec>
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