Pergunta de entrevista da empresa Wayfair

We are working on a clone of Google Docs that allows users to collaborate on documents. Many users can work on the same document at the same time. We have 100 instances of our service running on 100 different machines. Each document needs to be managed exclusively by one instance while it is in use, but one instance can handle multiple documents at once. We have a simple load-balancing system. Because each document has a random numeric ID found in the URL, we use the value of (id % num_instances) to route traffic. For example, with 100 jobs, traffic for document #314814196 is routed to the instance with index 96. How will this system perform as the usage grows?