Illumio Software Engineer Interview Questions
& Process

First up was a technical round focused on rate limiters, where I had to design and implement one. This probably touched on stuff like token buckets, leaky buckets, sliding window counters, distributed rate limiting, handling bursts, fairness, scalability, and API throttling use cases. Then, I had an onsite round with the hiring manager. We talked about problems I'd solved in past jobs and how well I understood streaming and messaging systems. This included event-driven architectures, Kafka/Kinesis/Pulsar, consumer groups, partitioning, backpressure, delivery guarantees (at-least-once vs. exactly-once), and the difference between real-time and batch processing. The last round was a design round, focusing on scalability and data structures. I had to design a system considering scalability (high throughput, fault tolerance, load balancing), use the right data structures and algorithms, and potentially talk about system components, communication patterns, handling big data or high I/O, and the trade-offs between latency, consistency, and complexity.

The interview started with a take-home online assessment. After waiting over a month, I was invited to the next stage. The second round was a technical screen with a Senior Staff Engineer from another team. I expected to discuss my take-home submission, but instead, it was a verbal interview covering general computer science topics and my background. The interviewer was quite rude and disrespectful, never introducing himself, and dismissive when I asked for clarification, often saying things like 'I already said that, did you not hear?'. He also made some odd personal remarks about my comprehension, and questioned why I was looking away from the screen, even though he was also looking at multiple screens.

The overall interview process was a mixed bag and gave me a bad impression of how the company manages its candidate pipeline. After completing the on-site panel, I was ghosted by three recruiters who had promised quick feedback within 48 hours. The interviewers were nice and explained the project, challenges, and future roadmap well. However, the recruiting team was disorganized with handoffs and didn't provide much guidance for the on-site panel. They were also completely unresponsive after I spent 4 hours at their office, plus my 2-hour commute. It wasn't a great experience, and I assume they rejected me, but I won't know for sure since it's been two weeks of me chasing three recruiters.