Definition
Adding more machines and spreading load across them (scale out), rather than buying a bigger machine.
How it works
Stateless services scale out trivially behind a load balancer; stateful stores need sharding or replication to scale out. It's the only way past the limits of one box and gives you redundancy, but adds coordination, data partitioning and network failure modes. Contrast with vertical scaling (a bigger box).
Common questions
What is Horizontal Scaling?
Adding more machines and spreading load across them (scale out), rather than buying a bigger machine.
How does Horizontal Scaling work?
Stateless services scale out trivially behind a load balancer; stateful stores need sharding or replication to scale out. It's the only way past the limits of one box and gives you redundancy, but adds coordination, data partitioning and network failure modes. Contrast with…
What is Horizontal Scaling used for in system design?
Stateless services scale out trivially behind a load balancer; stateful stores need sharding or replication to scale out. It's the only way past the limits of one box and gives you redundancy, but adds coordination, data partitioning and network failure modes. Contrast with…