Guided Notes

Scaling & Load Balancing

Scalability and elasticity, EC2 Auto Scaling, Elastic Load Balancing, and decoupling with SQS and SNS.

Scalability and elasticity

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Demand changes — a shop gets busy at lunch and quiet at night. Buying for the peak wastes money; buying for the average means outages at the peak.

• Scaling up (vertical) — a bigger instance. • Scaling out (horizontal) — more instances.

Elasticity means capacity follows demand automatically: add instances when it's busy, remove them when it's quiet, and pay only for what runs.