Building a social media platform like Twitter is a masterclass in distributed systems design. What starts as a simple CRUD application quickly evolves into one of the most challenging engineering problems in tech: delivering personalized, real-time content to billions of users across the globe.

In this post, we’ll walk through the architectural journey from a startup with 100,000 users to a global platform serving 1 billion people. Along the way, we’ll examine the critical tradeoffs that shape how we build, scale, and maintain such a system.