What does the term "scaling" mean in the context of MongoDB?

Scaling in the context of MongoDB is increasing a system's computing resources so it can handle more data and requests without a drop in performance.

In MongoDB the term covers two approaches:

#1. Vertical scaling (scale-up)

Increasing the power of a single machine:

• more CPU
• more RAM
• faster disks

The upside: simple. The downside: there's a limit, you can't keep "beefing up the hardware" forever.

#2. Horizontal scaling (scale-out)

Adding new servers to the cluster and distributing data/load across them:

• sharding, data is split across several nodes
• replication, read load is spread across secondary nodes

The upside: it can scale almost indefinitely. The downside: the infrastructure is more complex.

#The key idea

MongoDB was built from the start to be easy to scale horizontally, unlike many SQL DBMSs.

#Summary

Scaling in MongoDB is a set of ways to expand the system so it can handle larger volumes of data and requests. That can mean either strengthening a single server, or spreading the load across many machines.