Jr. Data Engineer Intern Interview Experience
Summary
I had an extensive interview for a Junior Data Engineer Intern position at BlueCopa, which included an online assessment and a challenging two-hour technical interview covering OOPs, SQL, DSA, and project discussions. While I handled most questions well, I faltered on project details and some Java concepts, and the final outcome was not provided in the post.
Full Experience
I applied for the Junior Data Engineer Intern position at BlueCopa through LinkedIn and, after my resume was shortlisted, received an invitation for an Online Assessment (OA). The OA, which lasted 90 minutes, was quite unique, comprising 6-8 modules covering Python, SQL, simple math and aptitude, English grammar, and memory-based tasks. I managed to complete this round in about 70 minutes.
The following day, I received notification that I had cleared the OA and was selected for the interview round. I scheduled my interview for a specific date, and to my surprise, the mentioned duration was only 30 minutes. To prepare, I reached out to a few current interns who indicated that questions would mostly focus on SQL, Python, and basic coding problems. This gave me confidence, especially given the short expected duration.
On the interview day, the interviewer started with introductions and a company overview before I introduced myself. He began by probing my knowledge of OOPs concepts, asking about the four pillars, the difference between overriding and overloading, and abstract classes versus interfaces. I answered all these questions with proper examples.
Next, he moved to SQL questions, which included discussions on GROUP BY, different types of JOINs in detail, the distinction between HAVING and WHERE, Indexing, and Normalization. He also presented a table and asked me to perform specific SQL operations on it. By this point, more than 30 minutes had passed, and I was satisfied with my performance, assuming the interview was drawing to a close. However, the interview remarkably stretched to almost two hours!
Following the SQL segment, he transitioned to Data Structures and Algorithms. He presented one easy and three medium-level problems: Longest Consecutive Sequence, Reverse Words in a String, Valid Anagram, and a variation of "Move Zeroes to End". After these, he asked several questions related to my projects. Mentally drained by then, I struggled to answer some of the project-related questions properly, especially regarding claims I had made about optimizing projects by "20%" and having "50+ active users", which unfortunately left a negative impression. Lastly, there were a few Java-related questions, such as the difference between JDK and JRE, and one more OOPs-based question that I couldn’t answer correctly.
Interview Questions (7)
Discuss the four pillars of Object-Oriented Programming (OOPs). Explain the difference between method overriding and overloading. Describe abstract classes and interfaces, and differentiate between them.
Explain the GROUP BY clause. Describe different types of JOIN operations in detail. Differentiate between HAVING and WHERE clauses. Explain the concepts of Indexing and Normalization in databases. Be prepared to perform SQL operations on a given table.
Find the length of the longest consecutive elements sequence in an unsorted array of integers.
Given an input string s, reverse the order of the words. A word is defined as a sequence of non-space characters. The words in s will be separated by at least one space. Return a string of the words in reverse order concatenated by a single space.
Given two strings s and t, return true if t is an anagram of s, and false otherwise. An Anagram is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.
A problem similar to 'Move Zeroes' but with a slight variation. The standard 'Move Zeroes' problem asks to move all 0's to the end of an array while maintaining the relative order of the non-zero elements.
Explain the difference between JDK (Java Development Kit) and JRE (Java Runtime Environment).
Preparation Tips
My initial preparation involved reaching out to a few current interns at BlueCopa to get an idea of the interview process. They informed me that the questions were generally based on SQL, Python, and some basic coding problems. This insight gave me confidence, particularly because the interview was initially slated for only 30 minutes, leading me to believe I could clear this round.