Definition
Centralised Service ( Distributed System)
A centralised service is a service whose request processing is concentrated at a single point, typically one server serving all clients.
Aggregate demand grows with the number of clients, but the central server’s processing capacity is limited. Adding capacity elsewhere does not remove this bottleneck unless the service’s work can also be distributed.
Example
One Server for All Users
Every user submits requests to the same server. Once demand approaches its capacity, requests queue and response times rise; adding more client computers does not increase service capacity.