Cloud computing

The on-demand delivery of IT resources over the internet with pay-as-you-go pricing. This is the Cloud Concepts domain, 24% of the exam.

What it is

Official page

Instead of buying, owning and running data centers and servers, you use compute, storage, databases and other services from a provider such as AWS, when you need them.

Key points

On demand: resources are provisioned in minutes, without a purchase order.
Pay as you go: you pay only for what you consume, with no minimum commitment for most services.
Elasticity: capacity grows and shrinks with demand.
High availability: services are built on multiple Availability Zones.

On the exam

If a question mentions paying only for what you use and provisioning in minutes, it is describing the cloud, not your own data center.

Six advantages

Official page

AWS sums up the value of the cloud in six advantages, which show up almost word for word in questions.

Key points

Trade fixed expense for variable expense: pay for consumption, not for data centers before you know how you will use them.
Benefit from massive economies of scale: the aggregate usage of many customers lowers pay-as-you-go prices.
Stop guessing capacity: scale up or down in minutes.
Increase speed and agility: new resources are a click away, so experimenting is cheap.
Stop spending money running data centers: focus on customers, not on racking, power and cooling.
Go global in minutes: deploy in multiple Regions with low latency.

On the exam

Match the scenario to the advantage: "demand is unpredictable" means stop guessing capacity; "launch in another country" means go global in minutes.

Service models

They define how much of the stack AWS manages and how much stays with you. The more abstract the service, the less you manage.

Key points

IaaS: infrastructure (network, machines, storage), e.g. Amazon EC2. You manage the operating system.
PaaS: a platform ready to run applications, e.g. AWS Elastic Beanstalk. You bring the code.
SaaS: complete software, used from the browser. You only use and configure it.

On the exam

Who patches the operating system? On EC2 the customer; on RDS or Lambda, AWS.

Deployment models

Where resources run: all in the cloud, part in the cloud and part on premises, or all in your own data center.

Key points

Cloud: every part of the application runs in the cloud.
Hybrid: connects on-premises infrastructure to the cloud, e.g. AWS Direct Connect, AWS Outposts.
On-premises (private cloud): resources in your own data center, with virtualization and management tools.

On the exam

"Keep legacy systems in the data center and extend into AWS" describes the hybrid model.

Shared responsibility

Official page

AWS is responsible for security of the cloud; the customer is responsible for security in the cloud. The split changes with the service.

Key points

AWS: hardware, network, physical facilities, Regions, Availability Zones and edge locations.
Customer: data, IAM permissions, encryption, guest operating system and applications (on EC2), security group configuration.
Shared controls: patch management, configuration management and training, each party at its own layer.
On abstracted services (S3, DynamoDB, Lambda), AWS runs the OS and platform; the customer handles data and access.

On the exam

Classic question: "who is responsible for X?". Physical and infrastructure is AWS; data, access and configuration belong to the customer.

Cloud economics

Why the cloud usually costs less than your own data center, and where the cost still depends on you.

Key points

CapEx to OpEx: upfront hardware investment gives way to variable expense.
On-premises costs: beyond the server, power, cooling, floor space, networking and people.
Rightsizing: choosing the right resource size for the workload, with no waste.
Licensing: BYOL (bring your own license) or license included in the service price.
Automation: less manual work and fewer errors, freeing the team.

On the exam

Rightsizing and turning off idle resources are the usual answers to cut costs without changing the architecture.

Cloud Adoption Framework

AWS CAF

Official page

AWS guidance for planning cloud adoption, organized in six perspectives, each with its own capabilities.

Key points

Business, People and Governance: business perspectives.
Platform, Security and Operations: technical perspectives.
Expected outcomes: reduced business risk, better ESG performance, increased revenue and operational efficiency.

On the exam

Know how to split the six perspectives into business (Business, People, Governance) and technical (Platform, Security, Operations).

Migration strategies

The 7 Rs

Official page

Ways to take each application to the cloud, from the simplest to the one that changes the application the most.

Key points

Rehost (lift and shift): move without changes. Relocate: move the whole virtualization platform.
Replatform: small tweaks, e.g. moving the database to RDS. Refactor: redesign to be cloud native.
Repurchase: switch to a SaaS. Retain: keep it where it is. Retire: turn off what is no longer used.
Tools: AWS Application Migration Service, AWS DMS and AWS SCT (see the Migration topic).

On the exam

"Move fast, without changing the code" is rehost. "Swap the database for a managed one, without rewriting the app" is replatform.