Vertical scaling, or scaling up, increases a single machine's capacity by giving it more CPU cores, memory, disk or network bandwidth.
Why it matters
It is the simplest way to gain performance because the application does not need to change. It suits databases and legacy software that cannot easily run on many nodes.
It has limits: the largest machine has a maximum size, costs rise faster than capacity, and a resize often needs a restart. It also leaves one machine as a single point of failure.
Example
A VPS with 2 vCPUs and 4 GB RAM struggles during peak hours. Resizing it to 4 vCPUs and 16 GB RAM requires a brief reboot, after which the database can cache more data in memory and queries get faster.
Common mistakes
- Scaling up repeatedly without finding the real bottleneck, such as a slow query.
- Resizing during peak hours and causing avoidable downtime.
- Treating a bigger server as a replacement for redundancy.
Related
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