In Week 2 , I shifted focus from high-level scalability concepts to how data is actually stored, retrieved, and optimized in real systems. The main goals this week were to: Build intuition around storage engines and access patterns Understand SQL vs NoSQL trade-offs Learn where indexes and caching fit into system design Apply these ideas by designing and implementing a User Profile Service Compared to Week 1, this week went deeper into backend fundamentals—and required slowing down to truly understand what happens under the hood. Key Learnings from Designing Data-Intensive Applications — Chapter 3 Chapter 3 (Storage & Retrieval) was significantly more challenging than earlier chapters—but also much more rewarding. Storage Engines: Why Data Layout Matters One of the biggest takeaways was that databases are not magic . They rely on concrete data structures that directly impact performance.…