GIS services enabled the use of cross platforms between different environments. Now, they can be consumed by a variety of clients from different software. The classical one-to-one model of having a dedicated instance for each connection doesn't fit anymore. It was inefficient to have a new instance for every established connection; it is as if you are opening a new ArcMap document every time. The GIS services have high affinity, and they tend to consume processing and memory power rapidly, so there must be a way around it. Another model was required to be plugged into Server to manage more connections with the available limited resources. Therefore, Esri introduced the pooling technology into Server for the first time in 2007 and it was revolutionary. This model allows each connection to use a GIS service instance for a certain amount of time, which could span from milliseconds to minutes. Each instance can serve one connection at a time, for example, if one user is using ArcMap...