Klaviyo Full Stack Engineer interview with API design and system improvement rounds

My first contact was a quick recruiter screen. After that, I received the CodeSignal link for the online assessment. Once I completed it, the process moved into a longer onsite structure covering past work, technical thinking, and collaboration.

The onsite included several technical and behavioral interviews. In one round, I went deep into past work and system design decisions, explaining the architecture and the reasoning behind the trade-offs. Another focused on leadership and behavioral topics, including conflict resolution and decision-making in complex situations.

I also had an API design and best-practices coding session. It went beyond algorithm problems and asked me to design and build a small API or system from scratch. A system design enhancement round followed, where I analyzed an existing design and suggested improvements for scalability, reliability, trade-offs, and edge cases.

There was a lot to fit into the overall experience, but the format felt practical and close to the job. I didn't get an offer. During the system improvement questions, I realized I was being evaluated on how I handled unknowns within a particular structure, not only on whether my answers were correct.

Location: Boston, MA. Overall feedback: Positive. Offer status: No offer.