Which would be the LEAST desirable architecture option for a database that requires a high degree of scalability?

A one-tier architecture, which places the entire database system on a single layer or machine, is the least desirable option for a database that requires a high degree of scalability. This is primarily because a one-tier setup does not allow for the distribution of workload across multiple servers or resources. As the number of users or transactions increases, the single server may struggle to handle the load, leading to performance bottlenecks and reduced efficiency. In a scalable environment, it’s essential to be able to add more resources seamlessly, which is not possible with a one-tier architecture.

On the other hand, two-tier and three-tier architectures distribute the application and database layers, allowing for better management of requests and load balancing among multiple servers. Cloud-based architectures also offer significant scalability by leveraging infrastructure as a service (IaaS) or platform as a service (PaaS), which can easily scale resources up or down based on demand. Thus, a one-tier architecture fundamentally limits the ability to scale effectively, making it the least suitable choice in scenarios where high scalability is critical.