I began by outlining a high-level architecture for the chat application, focusing on scalability and real-time messaging. I discussed using WebSockets for continuous communication and a microservices architecture to isolate different functionalities like user management and message storage.

The interviewer encouraged me to elaborate on data storage and suggested considering various databases. I initially suggested a relational database but then pivoted to NoSQL for its flexibility with chat data.

The interviewer seemed engaged but pressed me on load balancing and handling message delivery guarantees, which I struggled to detail adequately.