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Path 02 / Scaling & elasticity

Make room
for the next visitor.

Reliable systems need enough capacity to serve their users. Cloud architecture offers different ways to respond to growth.

Three ideas to know

  1. Scalability: the ability to handle a larger workload by adding capacity. Vertical scaling increases resources on one server; horizontal scaling adds more servers.
  2. Elasticity: adjusting capacity as demand rises and falls. Automated scaling policies can help match available resources to changing demand.
  3. Load balancing: distributing incoming requests across multiple targets. Health checks help identify which targets can receive traffic.
They work together. A load balancer distributes traffic, while a scaling mechanism changes the number or size of the resources serving it. A load balancer alone does not create new servers.

A simple example

A learning website gets busy before an exam. More application servers can be added as demand increases, and removed after traffic falls. The load balancer routes requests across available healthy servers.

Quick knowledge check

Which term describes capacity increasing and decreasing with demand?

Choose an answer to check your understanding.

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