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Practice These Hadoop Interview Questions and Ace Your Interview

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Practice These Hadoop Interview Questions and Ace Your Interview

If you’re interviewing for a position that’ll require you to process and manipulate large volumes of data — from gigabytes to petabytes — it’s very likely that you’ll use Hadoop in some capacity. Professions like Data Engineer, Data Scientist, Big Data Analyst, Big Data Software Engineer, Business Intelligence Specialist, and more all use Hadoop to help companies make data-informed business decisions.

One of the best ways you can prepare for Hadoop interview questions is to set up a mock interview and practice answering as many Hadoop-related questions as you can before your real interview. You could ask a friend or family member to help out and play the role of the interview, or you can simply practice saying your answers out loud in a mirror. 

Here are 15 popular Hadoop interview questions to help you get ready for the big day.

1. What is Hadoop, and what are its primary components?

For this question, you can say that Hadoop is an infrastructure that includes tools and services for processing and storing big data. It helps companies analyze their data and make more informed decisions.

The primary components of Hadoop include:

  • Hadoop Distributed File System (HDFS)
  • Hadoop MapReduce
  • Hadoop Common
  • YARN
  • PIG and HIVE — components of data access
  • HBase — for storage
  • Ambari, Oozie, and ZooKeeper — for managing and monitoring data
  • Thrift and Avro — for serializing data
  • Apache Flume, Sqoop, Chukwa — for integrating data
  • Apache Mahout and Drill — for data intelligence

2. What are the core concepts of the Hadoop framework?

Hadoop is based on two concepts: HDFS and MapReduce. HDFS is a file system for storing data across a distributed network that enables parallel processing and redundancy. 

MapReduce is a programming scheme for the processing of large datasets. It consists of two functions or processes: Map segregates datasets into tuples, and Reduce further refines this data to yield a final, culled result.

3. What are the most common input formats in Hadoop?

Hadoop uses three common input formats. The default format is the Text Input Format, which is the base class for all file-based input formats. It specifies the input directory where the data files are located. The Sequence File Input Format is dedicated to storing sequences of binary key-value pairs. And the Key Value Text Input Format treats each input line as a separate record and reads plain text files.

4. What is YARN?

YARN stands for Yet Another Resource Negotiator and is the interface in Hadoop for leveraging the various processing systems (MapReduce, Spark, and others ) on the available data resources.

5. What is Rack Awareness?

Rack Awareness is an algorithm NameNode uses to determine the pattern for blocking: the most efficient way to leverage storage and bandwidth resources based on the topology of the network..

6. What are active and passive NameNodes?

NameNodes are objects that manage the filesystem tree and the file metadata.  A Hadoop system with high availability contains both Active and Passive NameNodes to provide redundancy. The Hadoop cluster is run by the Active NameNode, and the standby, or Passive NameNode, stores the data of the Active NameNode.

If the Active NameNode ever crashes, the Passive NameNode takes over. This means that the failure of a NameNode won’t cause the system to fail.

7. What are the schedulers in the Hadoop framework?

The Hadoop framework contains three schedulers: the Capacity, Fair, and FIFO systems. The FIFO scheduler simply orders jobs in a queue based on their arrival time and processes them one at a time. The Capacity scheduler has a secondary queue that will run smaller jobs as they arrive. Fair Sharing dynamically allocates resources to jobs as needed.

8. What is Speculative Execution?

It’s a frequent occurrence for some nodes to run slower than others in the Hadoop framework, and this constrains the entire application. Hadoop overcomes this by detecting or speculating when a task is running slower than usual and launching an equivalent backup. The task that completes first is accepted, while the other is killed. This is known as Speculative Execution.

9. What are the main components of Apache HBase?

Three components make up Apache HBase. They are:

  1. Region Server, which forwards clusters of regions to the client using the Region Server. This occurs after a table divides into multiple regions.
  2. HMaster, which is a tool that helps manage and coordinate the Region Server.
  3. ZooKeeper, which is a coordinator in the HBase distributed environment that provides fault tolerance by monitoring the transaction state of servers. 

10. What is Checkpointing?

Checkpointing is a procedure of producing intermediate backups to guard against data loss and maintain efficiency. In Hadoop, the fsimage file contains the entire filesystem metadata. In the checkpointing process, a secondary NameNode creates a new merged fsimage file based on the existing fsimage file in memory and edits received from transactions on the primary NameNode.

11. What are some best practices for debugging Hadoop code?

The effort of isolating a problem can often be streamlined by implementing several practices to make data and processes of the system more transparent. These can include:

  1. Capturing logs specific to input and output processes
  2. Carefully consider instances in which exceptions are raised or not and how they might be useful in adding context to a situation
  3. Use counters to monitor task execution and other status and summary information to provide direction in error finding

12. What does RecordReader do?

A RecordReader is simply an iterator that provides a Map function with the records it needs for creating key-value pairs that then get passed to the Reduce phase of a MapReduce job.

13. In what modes can Hadoop run?

  • Standalone mode, a default mode for the purpose of debugging and development
  •  Pseudo-distributed mode, a mode for simulating a cluster on a local machine at a smaller scale
  • Fully-distributed mode, Hadoop’s production stage where data is distributed across different nodes on a Hadoop cluster

14. What are some practical applications of Hadoop?

Companies use Hadoop for a variety of tasks where big data is used. Some real-life examples of this include detecting and preventing fraud, managing street traffic, analyzing customer data in real-time to improve business processes, and accessing unstructured medical data in hospitals and doctor offices.

15. Which Hadoop tools enhance big data performance?

Several Hadoop tools significantly boost the performance of big data. You could mention any of these tools in your answer to this question: Hive, HDFS, HBase, Oozie, Avro, Flume, and ZooKeeper.

More interview support

Looking for more interview prep? Check out our guide to acing the technical interview, tips for answering behavioral interview questions, and our advice for the whiteboard interview. We also have a guide to interviewing on Zoom.

Our Career Center offers additional resources to help you get ready for your interview, as well as job-hunting advice for everything from resumes to cover letters to portfolios.And if you’re looking for classes to take to learn new skills, visit our catalog for a list of available courses.

Word of the Day: fugue

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This word has appeared in 33 articles on NYTimes.com in the past year. Can you use it in a sentence?

Emerging Music Stars

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Who are the promising teenage musicians in your community?

Practice These Selenium Interview Questions to Prepare For Your Technical Interview

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Practice These Selenium Interview Questions to Prepare For Your Technical Interview

If you’re looking for a job as a QA Engineer, Test Automation Engineer, QA Analyst, or User Acceptance Tester, part of the interview process will likely include some questions on Selenium, one of the most popular and powerful test automation tools for web applications.

The best way to prepare for Selenium interview questions is by reviewing potential questions you might be asked and practicing answering them in a mock interview setting. You can do a mock interview on your own or ask someone to play the role of the interviewer and read off questions to you. If you practice on your own, you might want to consider filming yourself so you can play back the recording and see how you did. 

To help you get ready for your technical interview, here are 15 Selenium interview questions you can review, along with tips on how to answer them.

1. What are the components of Selenium Suite?

Selenium Suite consists of four components, including:

  • Selenium IDE, a set of tools that include a Firefox, Chrome, and Edge plugin for building tests in the browser and exporting them.
  • Selenium Remote Control, a server that controls the embedded Selenium browser. You can write tests in various programming languages to interact with it.
  • Selenium Web Driver, a programming interface for Selenium. You can write tests with it in various programming languages, and it interacts natively with the web browser. Selenium Web Driver isn’t a server like Selenium Remote Control.
  • Selenium Grid, a tool that allows tests to be run simultaneously on multiple devices or web browsers in parallel.

2. What is an exception test in Selenium?

You write an exception test in Selenium when you expect something to fail and throw an exception. Exception tests pass when the code throws the specific exception targeted by the test.

3. What is Selenese?

Selenese is the language used for writing test scripts in Selenium. It consists of commands that instruct the Selenium engine to perform certain tasks. There are three categories of these commands:

  • Actions. These commands interact directly with the browser.
  • Accessors. These commands retrieve data from the application and store them in variables.
  • Assertions. These commands compare the state of an application with the expected state.

4. What is a locator in Selenium?

A locator is a command in Selenium that allows you to select, interact with, and retrieve data from elements on a web page. Selenium has many types of locators to choose from, including ID, class, Name, XPath, LinkText, and DOM.

5. What is an assertion in Selenium?

Assertions verify that the state of an application matches the intended design outcome. 

For example, when a user clicks a button, you expect a modal to be visible. Types of assertions include assert, verify, and waitFor.

6. What type of tests does Selenium support?

Selenium can be used for these types of tests:

  • Functional testing. All the following testing types are categories of functional testing, which test that an application functions according to the business requirements.
  • Regression testing. This tests that there are no side effects or bugs when new code is introduced into the application.
  • Smoke testing. This tests that the critical parts of the app function correctly.
  • Sanity testing. This tests that specific parts of the app function correctly in detail after a code change.
  • UI testing. This tests that the graphical elements of the application are displayed properly.
  • Database testing. This tests that the data displayed in the app is in sync with the data in the database.
  • Cross-browser testing. This tests that the application functions correctly and looks the same across different browsers.

7. What is a data-driven test in Selenium?

Sometimes it’s necessary to test multiple sets of input data within a field of an application. Instead of writing a custom test for each set of data, this data can be stored separately and use the same test for each set. You can store this data in Excel files, CSV files, XML files, or database tables.

8. What’s the difference between assert and verify in Selenium?

While both commands check if a condition is true or false, assert will stop the test if a condition is false and verify continues through the rest of the test case whether the condition is true or false.

9. How do you handle keyboard and mouse interactions in Selenium?

You do this with the Actions API. This API contains classes for executing keyboard and mouse events, as well as pen and scroll wheel actions.

10. What are some of the technical challenges with Selenium?

When discussing technical challenges associated with Selenium, you may want to work in some examples from your past work. You can also highlight how you dealt with these challenges, which gives the hiring team a glimpse into your critical thinking process. Here are a few ideas to get you started:

  • Selenium testing only works with web-based applications and requires third-party tools to test desktop and mobile apps.
  • Selenium supports capturing images or screenshots but requires third-party tools for comparing images.
  • Selenium doesn’t have built-in reporting tools or test management. For these, you have to use third-party tools.
  • While some tests can be written without programming knowledge using Selenium IDE, most will require you to know a programming language to customize them.

11. What types of exceptions can you expect in Selenium?

This is a question that would best be answered by referencing specific examples, a few exceptions that could be addressed include: 

  • TimeoutException. This is thrown when a command doesn’t complete in a specific amount of time.
  • NoSuchElementException. This is thrown when an element is not found on the web page.
  • ElementNotVisibleException. This is thrown when an element is not visible on the web page.
  • StaleElementException. This is thrown when an element has been deleted or is no longer attached to the DOM.
  • JavascriptException. This is thrown when executing JavaScript supplied by the user.

12. What is XPath?

XPath is a language used to query XML documents. Since HTML is based on XML, it’s one of the languages that can locate elements on a web page with Selenium.

13. What’s the difference between driver.close() and driver.quit() in Selenium?

In Selenium, driver.close() closes the currently active window in the browser, and driver.quit() closes all browser windows and should be used carefully.

14. What navigation commands are supported by Selenium?

There are four navigation commands supported by Selenium. They are:

  • navigate().back(). This command navigates to the last visited page in the browser history.
  • navigate().forward(). This command navigates to the next page in the browser history.
  • navigate().refresh(). This command reloads the current page.
  • navigate().to(). This command navigates to a specific URL.

15. What is pause used for in Selenium IDE?

This feature is especially useful when creating new tests or debugging tests. It’ll stop the test when an exception occurs so you can examine the statement that caused the exception, correct it, and continue the test.

More interview resources

If you’re looking for additional ways to prepare for your interview, check out our complete guide to the technical interview and our advice on answering behavioral interview questions. We also have tips for the whiteboard interview. And if you’re interviewing over Zoom, check out our Zoom interview advice.

Our Career Center provides more interview support, along with job-hunting resources for resume and cover letter writing, creating a portfolio, networking, and more.If you’re looking to learn a new skill or expand on your existing knowledge, take a look through our full course catalog.

Free February 2023 Wallpaper & Instagram quote

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Free February 2023 Wallpaper & Instagram quote

Free February 2023 Wallpaper & Instagram quote

Free February 2023 wallpaper is here!

It’s time for the first flowers of 2023. I know it may be a little bit early as we are still in the middle of winter; however, I hope this wallpaper will warm you up and remind you that spring will be here soon! Let them be my valentine’s gift for you.

Each wallpaper download from February 2023 includes:

  • Desktop wallpaper x3 (plain, with the calendar, and with a quote)
  • Phone wallpaper x3 (plain, with the calendar and with a quote)
  • Tablet wallpaper
  • Instagram ready quote

New!

From now on, monthly wallpaper comes with three mobile versions – with a calendar and quote for your lock screen and a darker one to use as a matching background. One of you has requested this option (Thank you, Linsey!), and I’m more than happy to add it. If you have any other ideas about what we can add or change in monthly wallpapers, let us know in the comments or contact us via the contact page.


Quote for February 2023

Love is in the air, so the only right choice for this month was a quote full of love. I wanted it to look like a valentine’s day card or a love letter from me to you. Share it on your social media and tag people you love to spread some positive energy during those cold winter days.

To the world you may be one person, but to one person you are the world

P.S the square image is also included in the download package below! Feel free to post it on your Instagram.



Looking for more? Check our previous wallpapers!

The free download includes three desktop options – one with the calendar and one without the calendar, and one with a quote. There is also a wallpaper for tablets and three options for the phone. We have also included an Instagram-ready square with the weekly quote.

FOR PERSONAL USE ONLY.

NOTE: This wallpaper is available as a free download through February 28, 2023 only. After that, a $5 download fee applies.


Huge Wallpaper Bundle

Grab all the 2022 wallpapers in one Huge wallpaper bundle. 12 unique designs for your computer, phone, and social media.



What font is it?

If you are curious about what font I’m using this month, let me help! Today’s classic is Sunflower, and you can find it in a great bundle I purchased last year. For the script part, I’m using the Dear Jana font, one of the few handwritten fonts that are easy to read.


Your voice matters!

If you have your favorite quotes and would like them to appear on the next free wallpaper, make sure to post them in the comments below or send us your ideas via email.

Enjoy!


P.S This post includes affiliate links so by clicking them you are supporting us. Thanks!

What Do We Do Today That Will Make Us Cringe in the Future?

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Wearing Crocs? Eating meat? Posting selfies? Binge-watching TV? What do you think our future selves will be embarrassed by?

Word of the Day: avocation

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This word has appeared in six articles on NYTimes.com in the past year. Can you use it in a sentence?

Top 15 Git Interview Questions (& Answers) to Help You Ace Your Technical Interview

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Top 15 Git Interview Questions (& Answers) to Help You Ace Your Technical Interview

Almost every development team depends on Git for version control and seamless collaboration between team members. It’s the industry standard for tracking changes in any set of files. So if you’re pursuing a position on a dev team — from Software Developer to DevOps Engineer to Technical Writer — experience with Git will likely be a prerequisite for the job. And it’s more than likely that you’ll be asked questions to test your skills and knowledge of Git during your technical interview

One of the best ways to prepare for an interview is to review commonly asked questions and practice answering them out loud. You can practice on your own or ask someone to set up a mock interview with you so you can practice answering questions in an interview-like environment. All this practice will help you feel less nervous when the time comes to interview in front of your potential new employer.

Here are 15 Git interview questions, along with tips on how to answer them, so you can start preparing for your upcoming interview.

Learn something new for free

1. What are branches, and what command creates a new branch?

C1 – – – C2 – – – C3

Above is an example of a simple commit history, in which C1 is the first commit (version), C2 is the second commit, and C3 is the third commit. This is an example of a master branch. Any new branches that get created are called the feature branch.

To create a new branch, you use the git branch command, and to view all the local branches, use the git branch command. The current branch is marked with an asterisk (*).

2. How often do you commit when using Git, and do you review files before committing?

You should be committing as frequently as possible. A good practice is to commit after every new feature as long as it can be done cleanly without breaking anything that already exists. Remember to leave a detailed message about your commit.

3. What are your best practices for writing commit messages?

For this question, the interviewer is looking to see if you’re consistent across your commit messages. You could talk about how you follow a template for each commit message within a project, which is one of the best practices for writing commits. It allows you to quickly identify and get some details about the commit without needing to do extra searching.

4. What’s the difference between git merge and git rebase? Which method do you prefer?

The two commands allow developers to incorporate changes from one branch into another. git merge allows for the creation of a new “merge commit” occurring between the master and feature commit. The command joins the two (or more if needed) together. For example, git merge will add changes to the current branch. Whereas git rebase can reapply the feature commit on top of the main branch.

So the major difference between the two is how the history gets managed. With git merge, the history of branches remains the same but can subsequently leave clutter from unnecessary old commits. And with git rebase, the main history is partially forfeited in favor of the feature history.

As for answering your technique preference, there’s no correct answer — just as long as you can prove your point. However, there’s some scrutiny with rebasing when working in large teams because you may inadvertently rewrite public commits. But both methods can be effective. Look into the “golden rule of rebasing” for more information.

5. What’s the difference between Git and GitHub?

While there are several differences between Git and GitHub, your interviewer is likely looking for you to point out that Git is a software focused on version control and code-sharing, whereas GitHub is a hosting service for Git repositories. 

You can also discuss how Git is a command-line tool that’s installed locally on a system, and GitHub is a graphical user interface that’s hosted on the web. You can check out our article Getting Started with Git and GitHub Desktop to learn more key differences between Git and GitHub.

6. Do you use the command line with Git?

The command line is a text interface for the computer’s operating system. It’s a useful tool for developers to work with system files, among other tasks. Git can be used with graphical user interfaces (GUIs), like GitHub, or it can be used with the command line. All Git commands can run on the command line. However, this isn’t the case for GUIs. So even if you don’t know Git all that well, having proficiency with the command line is a good skill set to show interviewers that you have the capability to, at the very least, work with Git.

7. When should you use git push compared to when you use git pull?

git push is used to upload content from one repository to another. For example, you can push content from a local repository into a remote repository.  

git pull is used to retrieve and integrate content from another repository.  For example, you can pull content from a remote repository into a local repository.

8. What command do you use to return to a previous commit?

To return to a previous commit on a private, local repository, you’ll first want to run git log to pull up the branch’s history. Then, after identifying the version’s hash you want to go to, use the git reset command to change the repository to the commit.

For a public, remote repository, the git revert command is a safer option. It’ll create a new commit with the previous edits rather than delete commits from the history.

9. Has there ever been a time when you worked from multiple machines or with multiple developers? How did you like it? What did you find most challenging?

To answer this question, you can talk about your workflow. For example, explain how you’ve used Git in the past as your version control system for working between machines or sharing with multiple developers.

10. What methods do you use to clean up your feature branches?

For this question, you can mention these three commands. 

  1. git merge --squash is a command that can merge multiple commits of a branch.
  2. git commit --fixup marks the commit as a fix of the previous commit.
  3. git rebase -i --autosquash is a rebase type of squash for merging multiple commits.

11. What are Git attributes used for?

Git attributes allow programmers to try different merge strategies within the files or directories of a project. Attributes are set on paths so that when certain settings are applied along the path, the attribute can perform requests. Git attributes can also perform requests when exporting your project.

12. Have you ever done debugging with Git? How did you do this?

To debug with Git, you use git bisect to identify the first commit to introduce a bug by using automatic binary search. And git blame identifies the author of a commit, while git grep searches for any string or regular expression in any of the files in the staging area.

13. Have you ever encountered a merge conflict? How did you go about resolving it?

Merge conflicts happen when there are competing changes within the commits, and Git is unable to automatically determine which changes to use. Merge conflicts can be resolved by editing the file that has the conflict. And once the edits get made, add and commit the file.

You can read more about merge conflicts in this GitHub article.

14. Explain Git hooks.

Git hooks are custom scripts that can run when certain actions occur. There are two types: client-side hooks and server-side hooks. Git hooks can be written in any scripting programming language. They should be located within the hooks subdirectory of the .git directory.

15. What’s your Git workflow like?

Some programmers use Git every day, while some don’t use it at all. It can depend on the project and team size, but you should be using Git just about every day that you program, in an ideal world. So modeling your workflow around Git is a great practice to have.

A best practice to follow regarding the VCS is to continuously communicate with team members to ensure everyone follows the same Git conventions. 

More interviewing resources

If you need to refresh your Git skills more before your interview, check out our Learn Git & GitHub course. In this course, you’ll review the most commonly used Git commands and be introduced to GitHub features that are helpful for teams and enterprises. You can also check out our Getting Started with Git blog. 

For more interview prep, read our tips on answering technical and behavioral interview questions and check out this complete guide to acing the technical interview. Looking for more? Our Career Center has even more interview and job-hunting advice and tips, and be sure to check out our full course catalog if you’re looking to learn a new technical skill.

What’s Going On in This Picture? | Jan. 30, 2023

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Look closely at this image, stripped of its caption, and join the moderated conversation about what you and other students see.

Top 3 Biggest Innovations for 2023

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Top 3 Biggest Innovations for 2023

 

2023 is a year in which important innovations are expected that will help with climate change and improve people’s quality of life. Based on articles from sites specialized in innovation and technology, we would like to present the 3 innovations, among many, that we think will most impact our day-to-day.

 

It is very important to emphasize that the results that we expect today are the fruit of years of study, research, and work by many people who seek new solutions to provide greater benefits to the planet and communities, through their commitment.

 

 

And so, what do we expect for 2023?

 

Electric vehicles at more affordable prices (even without a driver)

As technology improves, charging points become more widespread and costs become cheaper, having more affordable electric cars is a reality that allows a greater part of the population to drive sustainably. “You can get GM cars today with a budget of $30,000. Tesla, for its part, even with a more expensive offer, presents the Model 3 starting at around $46,990; being this currently the best-selling electric car in the United States.

 

Image: Tesla

Another important topic in the automotive sector is autonomy, this year Uber plans to launch a fully driverless service. In fact, this is something that is already making waves in China, as you can see in the following video.

 

 

A greater presence of Virtual Reality and Augmented Reality

 

Large companies are already working on improvements to their products so as not to focus only on video games and attract consumers, allowing activities such as shopping, socializing, and exercising. The recent partnership between Meta and Microsoft will bring Office 365 applications to virtual reality. We will also see products with improved and more affordable experiences. For example, Tim Cook announced that Apple will offer augmented reality products.

 

Image: Google

 

According to the article, Top 18 New Technology Trends for 2023, published on the site www.simplilearn.com, “The AI market will grow to a $190 billion industry by 2025 with global spending on cognitive and AI systems reaching over $57 billion in 2023.  With AI spreading its wings across sectors, new jobs will be created in development, programming, testing, support, and maintenance, to name a few. On the other hand, AI also offers some of the highest salaries today ranging from over $1,25,000 per year (machine learning engineer) to $145,000 per year (AI architect) – making it the top new technology trend you must watch out for!

 

Machine Learning the subset of AI, is also being deployed in all kinds of industries, creating a huge demand for skilled professionals. Forrester predicts AI, machine learning, and automation will create 9 percent of new U.S. jobs by 2025, jobs including robot monitoring professionals, data scientists, automation specialists, and content curators, making it another new technology trend you must keep in mind too!

Mastering AI and machine learning will help you secure jobs like:

Image: wikipedia

 

Other innovations expected by 2023, according to experts, would be:

– Advanced Wellness Gadgets

– 5G networks will be more widely available

– Folding devices

– First commercial spaces

– Quantum computing

– AI-powered robots and drones

– Smart cities

– Biotechnological Advance

– Takeoff of wind farms in the US

 

 

It is worth noting that these are predictions, and it is not clear if these innovations will come true or not, but if they are not 100% successful, for sure, due to the trend of the last few years, we will see great advances in these areas.

 

If you are interested in investigating more about the topic of Innovations, we leave you several publications with their points of view, very interesting to get an idea of the current panorama:

HERE ARE THE 5 BIGGEST INNOVATIONS TO EXPECT IN 2023