Cloud Concepts: Advantages, Design Principles, and Migration Strategy
Domain 1 (roughly a quarter of the exam) tests why organizations move to AWS and how they frame that move. You will not be asked to configure a VPC here - you will be asked to pick the right justification, framework, or migration strategy for a described business situation.
The advantages of cloud computing
Six advantages are examinable and each maps to a business outcome:
- Trade capital expense for variable expense - pay for what you consume instead of pre-buying servers.
- Benefit from massive economies of scale - AWS aggregates demand, so unit prices are lower than a single company can achieve in its own data center.
- Stop guessing capacity - provision what you need and resize; no idle hardware.
- Increase speed and agility - resources in minutes, so experiments are cheap.
- Stop spending money running and maintaining data centers - no facilities, power, or racking staff.
- Go global in minutes - deploy into multiple Regions quickly.
Elasticity vs scalability
Scalability is the ability to handle growth: vertical scaling makes one instance bigger, horizontal scaling adds more instances. Elasticity is automating that matching of capacity to current demand, including scaling in when demand drops. A question describing automatic removal of unused capacity at night is testing elasticity, not scalability.
Two frameworks that get confused
The Well-Architected Framework has six pillars: operational excellence, security, reliability, performance efficiency, cost optimization, and sustainability. It guides how you design a workload. The Cloud Adoption Framework (CAF) is organizational: it uses perspectives (business, people, governance, platform, security, operations) and phases to guide how a company adopts cloud. Upskilling staff, governance, and change management belong to CAF.
Worked example
A firm must exit its data center in six months. Workload A is a 15-year-old order system with no vendor support for changes; Workload B is a reporting tool the firm decides to replace with a SaaS product. Which migration strategies apply?
Workload A: rehost (lift and shift) - move the servers largely unchanged to hit the deadline, then optimize later. The deciding constraints are speed and risk, not elegance. Workload B: repurchase - abandon the custom build and buy a SaaS replacement. The other common strategies are replatform (relocate with minor optimization), refactor/re-architect, relocate, retain, and retire.
Traps that cost marks
- Choosing "refactor" whenever modernization is mentioned; refactoring is the slowest, most expensive option and rarely fits a hard deadline.
- Answering "reliability" for a question about cost of idle capacity (that is cost optimization or elasticity).
- Assuming cloud eliminates all fixed cost; support plans, committed Savings Plans, and data transfer still create predictable spend.
- Mixing CAF perspectives with Well-Architected pillars in the same answer.