  Load balancing plays a crucial role in many large scale systems. Several
different load balancing principles have been proposed in the literature, such
as Join-Shortest-Queue (JSQ) and its variations, or Join-Below-Threshold. We
provide a high level mathematical framework to examine heterogeneous server
clusters in the mean-field limit as the system load and the number of servers
scale proportionally. We aim to identify both the transient mean-field limit
and the stationary mean-field limit for various choices of load balancing
principles, compute relevant performance measures such as the distribution and
mean of the system time of jobs, and conduct a comparison from a performance
point of view.
