SDE-1 | Round 2 | PeopleStrong (DSA + Project + System)
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.