Suppose you need a database solution that supports flexible schema design and easy scalability. Which NoSQL database would be the most suitable choice and why?

Couchbase would be the most suitable choice in this scenario. It offers a flexible schema design with support for JSON documents, allowing developers to adapt the data model as needed without rigid schema constraints. Couchbase also provides seamless scalability through its distributed architecture and built-in caching capabilities, making it easy to scale both vertically and horizontally as application requirements evolve.