As we will see in the next sections, sharding is complicated and expensive operation-wise. It is important to plan ahead and make sure that we start the sharding process long before we hit our system's limits.

Some rough guidelines on when to start sharding:

• CPU utilization of <70% on an average
• I/O and especially write capacity is <80%
• Memory utilization <70% on an average

As sharding helps with write performance, it's important to keep an eye on our I/O write capacity and requirements from our application.