How would you approach designing a real-time notification system that can handle millions of notifications per second?

During my final year in college, I worked on a project to develop a real-time notification app for a campus event. We needed to ensure that students received updates instantly. We used a publish-subscribe model with Firebase for real-time data syncing. I designed the architecture to include a central server that would send notifications to a database, which would then push updates to users' devices. Through testing, we managed to handle a few hundred notifications at peak times, and feedback from users was positive, showing that they appreciated the timely updates. This project taught me the importance of scalability and user experience in system design.

As a volunteer for a local nonprofit, I helped design a notification system for events to keep volunteers informed. We used simple email and SMS notifications. I created a spreadsheet to track contacts and set up a system where I could send mass messages when new events were scheduled. This experience highlighted the need for a reliable system and prompted discussions about automating notifications in the future. Although we didn't handle millions of notifications, it was a great exercise in understanding user needs and the importance of clear communication, which can translate to larger systems.

In my first job as a junior developer, I was part of a team that developed a messaging feature for our app. While not directly related to real-time notifications, I learned a lot about handling data flow and ensuring timely message delivery. We used web sockets to allow users to receive messages instantly. I contributed by testing the system under load, which prepared me for handling scalability issues. This experience gave me insight into the challenges of ensuring that notifications are delivered promptly and reliably, which is crucial for user engagement.