Pushkar

Gone are the days when SDE 3 Low Level Design interviews were about writing a couple of classes and passing basic OOP checks. If you could draw a few UML diagrams, apply Singleton or Factory pattern you passed. Today LLD interviews expect you to design systems extensibility, correctness, and real-world constraints in mind, such as: 1. In-memory cache with eviction policies, and concurrency guarantees 2. Rate limiter with sliding window, token bucket, and thread safety 3. Subscription billing system with plans and retries 4. Notification dispatcher with ordering 5. Config-driven workflow or rules engine 6. In-memory spreadsheet and formula engine 7. Parking lot or inventory system with concurrent updates 8. Message queue with producers, consumers. LLD today is less about patterns on paper and more about designing code that won’t break at scale and under change.