What hardware is used to build large automated information systems?

Question

Database

Good evening!
Is it possible to design a system that provides acceptable performance under the condition of a large number of connected and, most likely, simultaneously working users in it (48,000 branches, each of them has about 1-5 workplaces connected to this system + an indefinite number of client connections "from outside" not related to a specific branch)?
In theory, this is a large-scale library IS that implements the following functions: a full-text database of literary works with a search through it; interlibrary loan; electronic delivery of documents. Built on a client-server architecture.
The IS consists of a data center (on which, in fact, the databases are running) and client computers connected to the data center (both service computers located in libraries and readers' computers working with the system from home). The system is operated through a web interface.
The bottleneck here, as far as I can tell, is the full text DB. Firstly, it is necessary to support a huge number of active user connections and process requests from them, and secondly, its purpose implies a gigantic size of this database, which further complicates the issue of system performance.
Actually, the questions are as follows:
1) What hardware resources, what kind of hardware should be available to make this system work?
2) How can a full-text database be organized to ensure performance at an acceptable level and implement the functionality of storing large texts with a search for them? Digging towards distributed databases, dividing one into several and distributing them over dedicated machines, for example?