Choosing the right database in the system design interviews is one of the most important decisions. The database selection impacts the design correctness and scalability of the system. There are many factors which might impact the decisions, but the most important ones are: Structure of the Data: Different databases support data models such as relational, document, key-value, graph, etc. The choice of database depends on which data model best fits the structure of your data. For example, a traditional relational database like MySQL or PostgreSQL might be appropriate if the data is highly structured and relational. A NoSQL database like Cassandra or MongoDB might be more suitable if the data is semi-structured or unstructured. Query Pattern: Understanding the types of queries and operations performed on the data helps select a database that can efficiently handle those operations. Are they read-heavy or write-heavy? Do they involve complex joins, aggregations, or full-text searches?...