Cost Optimization in Serverless NoSQL (DynamoDB/Firestore).

Senior level NoSQL architecture is about balancing trade-offs between performance, cost, and developer agility at massive scale.

At a senior level, you must understand the underlying storage engine (e.g., LSM-Trees). Unlike B-Trees used in SQL, LSM-Trees optimize for writes by appending data to immutable segments and using background compaction. However, this creates 'Read Amplification' and 'Write Amplification.' You must also master Single Table Design in systems like DynamoDB, where you use GSI (Global Secondary Indexes) and Overloading to satisfy multiple access patterns in a single request.