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20 Best NoSQL Interview Questions For Beginners and Experienced Developers

NoSQL Interview Questions

Hiring the Right NoSQL Developer

Looking for the right NoSQL developer for your organization can be a bit tricky. A piece of paper cannot always reflect the candidate’s skills. Thus, interviews are a must for hiring new talent for your organization. Having pre-set NoSQL interview questions can help decrease your burden as a recruitment officer, and helps in saving up on a lot of precious time.

However, countless number of candidates apply for jobs, making your job cumbersome, as you would be required to conduct those many interviews. To help combat this issue, HirinGuru provides employers with a platform, to help conduct technical screening, to find the right NoSQL developer for your organization. You can set yourself free from conducting manual interviews and assessments by using HirinGuru. 

10 Best NoSQL Interview Questions for Beginners

Some questions help the employer to differentiate a beginner from an experienced developer. Once the interview starts, the employer or recruiter starts with the most basic questions to assess your capabilities and knowledge. The ten best NoSQL interview questions are:

1. What is NoSQL?

NoSQL stands for Not Only SQL. It is a type of database that helps in handling and sorting out unstructured data. It is responsible for storing and retrieving data modeled in other means, apart from the usual tabular relations that are used in relational databases, such as SQL, Oracle, etc.

2. What are the features of NoSQL?

The main features of NoSQL are:

Simple API

NoSQL does not use the standard based query language. The interface is very user-friendly, making storing and querying of data very easy. There is a low-level data manipulation required.

Integrated Caching

NoSQL has the integrated ability to cache.

Replication

NoSQL allows automatic database replication.

Auto-sharding

NoSQL allows horizontal scaling i.e. adding servers instead of increasing the capacity of a single server. For this. NoSQL provides the feature of auto-sharding, which means that the data is spread automatically across various servers.

Dynamic schemes

NoSQL allows the Insertion of data without any predefined schema. This makes development much faster and reliable.

3. What are the advantages of the NoSQL database?

The NoSQL database has the following advantages:

  • Provides horizontal scalability
  • No predefined schema
  • Supports semi-structured and volatile data
  • Read/Write allowed
  • Supports BigData in Terra Bytes and Peta Bytes
  • Able to provide good support for analytic tools
  • Allows caching
  • Does not require expensive hardware machines to run on
  • Faster development life cycles

4. What are the challenges of using NoSQL?

The following are some of the challenges faced by NoSQL users:

  • GUI not available
  • Open-source platform
  • Narrow focus
  • Management challenge
  • Large size of document

5. Explain the transaction support by using BASE in NoSQL systems?

A NoSQL transaction is the execution of an application that consists of a series of operations that provide transitions between consistent states of the NoSQL data. With the help of BASE (Basically Available, Soft state, Eventual consistency), the availability of data is guaranteed, with a response to any request. It can be a failure too.

6. Explain the Polyglot Persistence in NoSQL?

The Polyglot persistence is an application that uses more than one core database technology to handle data storage needs. NoSQL works well with polyglot persistence because it minimizes the impedance mismatch and it allows large scale data to be stored. 

7. What is the CAP Theorem? How is it applicable to NoSQL systems?

The CAP Theorem states that in a distributed system, you can only have two out of the following three guarantees:

Consistency: all nodes in the cluster consist of consistent data and a read request results in the recent write from any node.

Availability: a non-failing node must always respond to requests fast enough.

Partition Tolerance: during network or node failure, the system continues to operate.

According to the CAP Theorem, you can only have CA, AP, or CP characteristics for any given system. The above-mentioned combinations can be used according to your requirements in NoSQL.

8. Compare NoSQL and RDBMS.

Properties of NoSQL are:

  • Cost-effective
  • Make use of distributed computing
  • Higher scalability
  • Support flexible schema
  • Able to process unstructured and semi-structured data
  • No complex relationships

Properties of RDBMS (Relational Database Management Systems) are:

  • Atomic values
  • All values in a column have the same data type
  • Each row is unique
  • The sequencing of columns is not important
  • The sequencing of rows is not important
  • Every column has its unique name
  • Integrity constraints helps in maintaining data consistency in multiple tables

9. Explain the difference between NoSQL and Relational database?

The differences between NoSQL and relational database lies in their building, the types of information they store, and how the information is stored. The relational databases allow data to be stored on multiple tables, with links established between these tables. All relational databases must fulfill the ACID (atomicity, consistency, isolation, and durability) properties. On the other hand, NoSQL is an open-source database platform that deals with big data.

10. When can you use a NoSQL database instead of a relational database?

NoSQL is the database of choice when big data has to be handled, along with overcoming the limitations of transactional databases. Also, when there is a need to handle structured, semi-structured, and unstructured data, NoSQL is the database of choice. If your client has required a higher availability on a high traffic website, then you must opt for NoSQL.

10 Best NoSQL Interview Questions for Experienced Developer

NoSQL interview questions for experienced developers are a lot different from beginners. These questions help the interviewer to evaluate the candidate’s problem-solving abilities and technical knowledge.

The NoSQL interview questions for experienced developers are:

1. What is the Oracle NoSQL database?

The Oracle NoSQL database is a horizontally scalable database that has multiple higher-level abstractions. They help support data management as binary key-value pairs, JOSN objects, and SQL-like tables. It can be run on-premise or as a cloud service platform. 

2. Does the NoSQL database interact with the Oracle database?

The NoSQL database can be run with the Oracle database to help in better data processing and management.

3. Explain the modes of operation that are supported by Flume?

Flume supports the following three modes of operation:

—Single node: used for basic testing

—Pseudo-distributed: used for the testing of more complicated flows on a single physical machine

—Fully distributed: used in building more complicated flows that are tested on a single physical machine. 

4. What do you know about Impala?

Impala is an MPP (Massive Parallel Processing) SQL query engine, written in C++ and Java, that is used in processing large volumes of data stored in a Hadoop cluster. It is an open-source software that provides the fastest way to access data stored in the Hadoop Distributed File System.

5. What are the benefits and drawbacks of Impala?

Impala has the following benefits:

  • Process data stored in the Hadoop Distributed File System at a much faster speed
  • No need for data transformation and movement as data is stored on Hadoop.
  • Easily access data stored in HDFS, HBase, and Amazon s3 just with the basic idea of SQL queries
  • Shortened process of writing queries
  • The Parquet file format is optimized for large scale queries

Impala has the following drawbacks:

  • There is no support for serialization and deserialization
  • No support for reading custom binary files; only text files can be read
  • The table needs to be refreshed whenever new records or files are added to the data directory in HDFS 

6. How to script a NoSQL database configuration?

The same NoSQL database configuration can be built for repeated testing. These commands can be scripted in several ways. One way is to use simple commands, such as java -jar kvstore.jar makebootconfig, and another way is to run individual CLI commands as separate shell command lines. A single CLI command is considered to be the trailing arguments in the command line.

7. How does NoSQL database budget memory?

The main consumer and manager of memory in a NoSQL database is the replication node. Each replication node uses a cache. This helps the NoSQL database to budget memory.

8. What scalability issues have you encountered so far with using a NoSQL datastore?

With this question, the interviewer is trying to assess your experience with NoSQL so far.

9. Describe an interesting project you have participated in? What makes it so interesting?

The interviewer is trying to find out about your work experience and exposure with NoSQL.

10. Tell us about a failed programming project decision you took? Why do you think it was a mistake? Give details.

The interviewer is trying to find out about your failures, and how you combated the issue. The interviewer wants to know if you realized your mistake and learned from it.

NoSQL Interview Questions Process – Bonus 

The interviewer does not start questioning a candidate about his skills right away. He gives him a few moments to adjust to y=the environment and get rid of the anxiety he may be facing. Once that is done, the interviewer starts with questions related to the candidate’s education and work experience. Once that is out of the way, the interviewer bombards the candidate with NoSQL database interview questions, starting with the basics, of course. Interviewers generally ask broad questions to test the candidate’s knowledge, in addition to checking their problem-solving skills. These questions are broadly divided into three parts. They are:

1. Technical questions 

These questions involve a technical discussion based on the candidate’s previous projects. The candidate may be asked to write codes on the whiteboard, or draw solutions, if need be.

2. Process thinking questions 

These questions help the interviewer to analyze the candidate’s thought process. This may involve problem-solving puzzles, design questions or simply discussing a technical issue. 

3. Problem-solving questions 

The interviewer may bring up a problem from their current project, and discuss it with the candidate, to help analyze the candidate’s problem-solving ability.

Hire the Best NoSQL Developer using HirinGuru 

HirinGuru provides a platform for employers to conduct a comprehensive assessment to help improve your recruitment process. This, in turn, would help to improve your organization’s interview to hire ratio. This comprehensive assessment includes aptitude tests, coding tests, domain tests, and ML Algorithm tests. This thorough assessment helps in testing the knowledge and skills required by the candidate to be hired for the job of a NoSQL developer. Those candidates who perform well and clear this assessment will be promoted to the second round of the recruitment process- the interviews. Candidates who performed below average will not be called for an interview, saving up on the employer’s time and efforts. Organizations usually have a pool of NoSQL database interview questions, which do get repeated during interviews.

The services of HirinGuru are not just limited to the field of AI and ML, other skilled technicians, such as engineers and data scientists, can also undergo a comprehensive technical screening. Furthermore, you can integrate your Applicant Tracking System platform with HirinGuru, to ensure the streamlining of all your hiring processes. If you cannot make up your mind regarding HirinGuru, you would be delighted to know, that they offer a 30-day free unrestricted access trial on their beta version. 

NoSQL Developer Job Trend in 2020

Recently, there has been an increase in the demand for personnel with database management skills. This demand extends beyond the web and software companies. In this competent field, candidates with a deeper understanding of NoSQL have an edge over the average NoSQL developers. Comparing different countries, China has the greatest number of people interested in this field, while Iran has the lowest number of people interested in this field. Looking at the interest graph from Google Trends, between August 2019 to July 2020, you can see that the results have been fluctuating all along- nothing consistent or exponential.

NoSQL Developer Job Trend

Source: Google Trends

NoSQL Developer Skills Evaluation and How to Find the Perfect Candidate 

Interviewing all candidates that apply for the position of NoSQL developer is just not humanly possible. To help save up on time and speed up the process of finding the right developer, you can use platforms, such as HirinGuru, to help conduct the technical screening of candidates. This comprehensive assessment would help you to identify the best NoSQL developers from the lot, who know the various concepts and technologies associated with NoSQL. Those candidates who have cleared the assessment phase can then be interviewed, to assess their knowledge and skills further. As discussed earlier, the interview consists of numerous questions to help assess and analyze the candidate thoroughly.  

Final Thoughts 

Conducting a thorough technical screening is a must before hiring any individual as a NoSQL developer. This is an essential step to ensure that only those candidates, who are deemed fit for the job, are interviewed. This saves up on the time and hassle of interviewing candidates who do not know the basics of this job. Various technical screening platforms, such as HirinGuru, take care of the initial screening process, while you, being the employer, can focus on the NoSQL interview questions.