Cloud Concepts
What this domain tests
Cloud Concepts questions ask you to explain why organizations move to the cloud and to name the models AWS uses to describe that move. You should be able to recite the advantages of cloud computing (trade capital expense for variable expense, benefit from massive economies of scale, stop guessing capacity, increase speed and agility, stop spending money running data centers, go global in minutes), and to separate closely related terms.
Terms that get confused
- Scalability is the ability to handle growth (scale up = bigger instance; scale out = more instances). Elasticity is automation that matches capacity to demand and removes it when demand falls.
- High availability survives a component failure with minimal downtime; fault tolerance keeps running with no interruption at all.
- IaaS / PaaS / SaaS describe how much of the stack the provider manages. Cloud, hybrid, and on-premises describe deployment models.
Also know the six pillars of the AWS Well-Architected Framework (operational excellence, security, reliability, performance efficiency, cost optimization, sustainability), the AWS Cloud Adoption Framework perspectives (business, people, governance, platform, security, operations), and the migration strategies known as the 7 Rs (retire, retain, rehost, relocate, replatform, repurchase, refactor).
Traps
Any answer offering increased capital expenditure or guessing capacity in advance is wrong. When the stem says demand is spiky and unpredictable, the answer is elasticity, not scalability. Do not confuse agility (speed of experimentation) with elasticity (automatic capacity matching).
Worked example
A concert-ticketing site gets a burst of traffic the moment seats go on sale. Design: an Elastic Load Balancer in front of an Auto Scaling group so capacity expands at the sale and contracts afterwards - elasticity plus cost optimization. Buying fixed servers sized for the annual peak and running them all year is scalability without elasticity, and wastes money.
Rule of thumb: if the wording is "automatically matches demand" or "shrinks when idle," choose elasticity; if it is "handles growth," choose scalability.