Before diving into Meteor, it is critical to understand what the event loop and the merge box are and how they can adversely affect your code. Both are relatively complex in the way that they were programmed, so we will focus on understanding the general concept.
The event loop is like a queue; it runs a series of functions one by one. Because functions are processed sequentially, each function effectively blocks others from being processed until the function is done.
In other words, the event loop functions much like a single-line conveyor belt where things are being inspected. For every inspection made, the line is stopped and nothing moves.
Meteor uses Fibers – a NodeJS library – to get around this ...