Summary
I interviewed for an SDE2/1 position at PeopleStrong, facing rounds on DSA, SQL, and core concepts. Despite my performance, I never received feedback from HR after multiple follow-ups, indicating a lack of offer.
Full Experience
My interview experience at PeopleStrong for an SDE2/1 role started with a single round. I have 3 years of experience.
The round began with a Data Structures and Algorithms section. The problem presented was to implement Binary Search to find a key element or, failing that, the immediate greater element. Initially, the problem statement felt a bit confusing. It sounded like they might want key or key+1, but it was later clarified that the goal was to return the immediate greater element. If neither was found, I was supposed to return -1. I adjusted my solution accordingly, and the interviewer seemed satisfied with my approach.
Next, there was a SQL section where I was asked to design Employee and Company entities. Following the design, I had to write a query to find the maximum salary in the Employee table associated with a specific company.
Finally, we discussed core concepts, specifically Kafka and Multithreading.
The interviewer was polite and very helpful throughout the process, which made the experience positive despite the initial ambiguity in the DSA problem. However, after the interview, I never received any feedback from HR, despite my persistent follow-ups with calls that went unanswered. This indicated to me that I likely did not receive an offer.
Interview Questions (2)
Implement binary search to find a key element or, if not found, the immediate greater element in a sorted array. If neither is found, return -1.
Design SQL entities for Employee and Company. Then, write a SQL query to retrieve the maximum salary from the Employee table, linked to a specific company.
Summary
I recently had my SDE-1 Round 2 online interview at PeopleStrong, which focused on a combination of DSA, project discussions, and system design. I am pleased that I was shortlisted for the next stage.
Full Experience
My second interview for the SDE-1 role at PeopleStrong was an online round covering Data Structures & Algorithms and project-related discussions. I received a 'shortlisted' result, moving me to the next stage. The interview started with an in-depth discussion on Project and CS Fundamentals. We deep-dived into HashMap internals, where I explained its structure using an array of buckets (which can be linked lists or trees), how hashCode maps to an index, different collision handling strategies, the significance of load factor and resizing, the equals contract, and the concept of fail-fast iterators. Following this, we talked about System health monitoring, discussing key metrics for hosts (CPU, memory, disk, net), applications (p50/p95 latency, error rate, RPS), and databases (connections, slow queries, locks). I also mentioned common tools like Prometheus and Grafana, along with health checks and uptime pings.
Next, we moved onto the Coding Questions. I was given three specific problems:
1. Linked List Cycle (detect + start node): The task was to detect if a cycle exists in a given linked list and, if so, return the node where it starts.
2. Word Ladder II (all shortest paths): I needed to find all the shortest transformation sequences from a beginWord to an endWord using a given wordList.
3. Convert number into words (up to 20 digits): This problem required converting a given integer into its English word representation, handling very large numbers up to 20 digits.
For each coding problem, I outlined my approach and discussed its time and space complexities. We also covered various edge cases. For Linked Lists, this included 0/1 node scenarios and cycles at the head or in the middle. For Word Ladder, we discussed cases with no path, large dictionaries, and avoiding revisiting previous levels. For the number-to-words conversion, we talked about 0, trailing zeros in chunks, and extremely large values.
Finally, I shared some tips that I felt were important during the discussion, such as stating complexities upfront. Specifically for Word Ladder II, I emphasized using level-by-level BFS and pruning to only consider minimal-distance parents. For HashMap, I made sure to mention the resize trigger and treeification as introduced in JDK 8 for high collision counts.
Interview Questions (5)
I was asked to discuss the internals of a HashMap, covering its underlying data structure (array + bucket with linked list/tree), how hashCode maps to an index, collision handling mechanisms, the role of load factor and resizing, the equals contract, and fail-fast iterators.
I was asked about designing a system for health monitoring. This included monitoring metrics at the host level (CPU, memory, disk, network), application level (p50/p95 latency, error rate, RPS), and database level (connections, slow queries, locks). I also had to mention common tools and practices.
Given the head of a singly linked list, detect if a cycle exists in it. If a cycle is present, return the node where the cycle begins.
Given a beginWord, an endWord, and a dictionary wordList, return all shortest transformation sequences from beginWord to endWord. A transformation sequence must change only one letter at a time, and each transformed word must exist in the wordList.
I was asked to implement a function that converts a non-negative integer into its English word representation. The input number could be very large, up to 20 digits, requiring handling billions, trillions, and beyond.
Preparation Tips
My preparation involved rigorous practice of Data Structures and Algorithms problems. I specifically focused on understanding the intricacies of HashMaps and Linked Lists, as well as graph traversal algorithms like BFS and DFS. Additionally, I reviewed core System Design concepts, particularly around monitoring and observability. I made an effort to practice articulating my solutions, complexities, and edge case handling clearly and concisely during mock interviews.
Summary
I interviewed for an SDE-1 Java Backend Developer role at PeopleStrong and successfully cleared the first round, which covered System Design, Data Structures & Algorithms, Core CS, and Java backend fundamentals.
Full Experience
I started the interview with a self-introduction, followed by a detailed resume walkthrough where the interviewer picked specific topics from my experience for Q&A. The round was comprehensive, focusing on Data Structures & Algorithms, System Design, and core Computer Science and Java backend questions.
Interview Questions (12)
I was asked to explain the key differences between Monolithic and Microservices architectural styles, outlining their respective advantages and disadvantages.
The interviewer asked for an explanation of the CAP Theorem, requiring me to define Consistency, Availability, and Partition Tolerance, and discuss its implications in distributed systems.
I had to describe the ACID properties (Atomicity, Consistency, Isolation, Durability) as they apply to database transactions.
I was asked to discuss various strategies and techniques to reduce API latency, including topics like caching, database optimization, asynchronous processing, Content Delivery Networks (CDNs), and load balancing.
The question involved explaining the working of the Circuit Breaker Pattern, specifically in the context of Resilience4j, and discussing its practical use cases in distributed systems.
I needed to explain different types of SQL indexes (Clustered, Non-Clustered, Covering, Composite), their advantages and disadvantages, and the underlying data structure used (B+ Tree).
I was asked to explain the differences between a Primary Key and a Foreign Key in relational databases.
I had to explain the difference between the final keyword and the finally block in Java.
The interviewer asked what a JSON Web Token (JWT) is, how it works, and its role in authentication and authorization processes.
I was asked to explain the key differences between authentication and authorization in the context of security.
I had to explain the differences between the @RestController and @Controller annotations in the Spring Framework.
Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', I had to determine if the input string is valid. An input string is valid if: open brackets must be closed by the same type of brackets; open brackets must be closed in the correct order; every close bracket has a corresponding open bracket of the same type. I was required to dry run the solution with inputs provided by the interviewer, covering multiple test cases and edge cases.
Preparation Tips
My preparation focused strongly on System Design basics and Java backend concepts. I paid particular attention to database optimization, especially indexes. I also made sure to understand Resilience patterns and the JWT flow. The DSA problem was of medium difficulty, primarily a stack-based problem.