Cross-cutting notes and exam extras

Foundational notes for AWS Certified Cloud Practitioner (CLF-C02). Read them in order the first time through, then use them as a revision sweep before you book.

11 study points. Everything here is exam-oriented: each point is a fact or a distinction that CLF-C02 items are built on. Test yourself against the practice exam once you can explain a section without re-reading it.

Extra Notes

Understanding the difference between Amazon S3 and Amazon EBS is fundamental. S3 is object storage, meaning you store complete files (photos, videos, backups, logs) and access them via HTTP. EBS is block storage, meaning it acts like a raw hard drive attached to a single EC2 instance where you can install an operating system or run a database. S3 is accessed over the network and can be reached from anywhere, while EBS must be attached to an EC2 instance in the same Availability Zone.

EBS data is automatically replicated within the same Availability Zone, not across AZs. This protects you against a single hardware failure but not against an entire AZ going down. To protect against AZ-level failures, you should regularly create EBS snapshots, which are stored in S3 and replicated across multiple AZs. You can then restore a snapshot into a new EBS volume in any AZ within the same Region, providing a solid disaster recovery strategy.

AWS Well-Architected Framework consists of six pillars: Operational Excellence, Security, Reliability, Performance Efficiency, Cost Optimization, and Sustainability. Each pillar provides a set of design principles and best practices for building cloud applications. Before building anything on AWS, reviewing the Well-Architected Framework helps you avoid common mistakes and design systems that are secure, resilient, and cost-effective from the start.

Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) represent different levels of abstraction in cloud computing. EC2 is IaaS because you manage the operating system and everything above it. Elastic Beanstalk is PaaS because AWS manages the platform and you just deploy your code. SaaS would be something like Gmail or Salesforce where you simply use the application. As you move from IaaS to SaaS, AWS takes on more responsibility and you take on less.

The AWS Global Infrastructure is designed to deliver low latency, high throughput, and highly redundant networking. As of today, AWS operates in dozens of Regions worldwide, each with multiple Availability Zones. New Regions are regularly announced to serve growing customer demand in different geographies. When choosing a Region, consider four factors: compliance requirements (some data must stay in certain countries), proximity to your users (lower latency), available services (not all services are in all Regions), and pricing (which varies by Region).

AWS CloudFormation and AWS CDK (Cloud Development Kit) are both infrastructure-as-code tools, but they work differently. CloudFormation uses JSON or YAML templates to declare your resources. CDK lets you define the same infrastructure using familiar programming languages like TypeScript, Python, or Java, and then synthesizes CloudFormation templates behind the scenes. If you prefer writing code over writing configuration files, CDK is an excellent choice that still benefits from CloudFormation’s reliable provisioning engine.

AWS Systems Manager is a collection of tools for managing your EC2 instances and on-premises servers at scale. It includes Session Manager for secure shell access without opening SSH ports, Parameter Store for managing configuration data and secrets, Patch Manager for automating OS patching, and Run Command for executing scripts across fleets of instances. Systems Manager eliminates many of the tedious operational tasks that consume time in traditional environments.

Amazon Route 53 is AWS’s scalable Domain Name System (DNS) service. It translates human-readable domain names like www.example.com into IP addresses that computers use to connect. Route 53 also offers health checking and traffic routing policies such as latency-based routing, geolocation routing, and weighted routing. For example, you can configure Route 53 to route users to the AWS Region closest to them, reducing latency and improving the user experience.

AWS Migration services include the AWS Migration Hub for tracking migrations, the AWS Application Discovery Service for planning, DMS for database migration, and the AWS Snow Family (Snowball, Snowball Edge, Snowmobile) for physically transferring large amounts of data. If you have 100 terabytes of data to move to AWS, shipping it on a Snowball device can be faster and cheaper than transferring it over the internet. AWS provides a full suite of tools to support every phase of your cloud migration journey.

The AWS Shared Responsibility Model is the single most important concept for the Cloud Practitioner exam. Remember it this way: AWS manages the security of the cloud (hardware, software, networking, and facilities), while you manage the security in the cloud (your data, access management, application configuration, and encryption). The exact split depends on the service type: with EC2, you manage everything from the OS up; with Lambda, AWS manages everything except your code and the IAM permissions you assign to it.

Cost optimization on AWS is an ongoing practice, not a one-time exercise. Regularly review your resources with Cost Explorer and Trusted Advisor. Use Reserved Instances or Savings Plans for predictable workloads. Leverage Spot Instances for fault-tolerant batch processing. Right-size your instances by matching them to actual usage. Set up AWS Budgets alerts to catch unexpected spending early. Delete unused resources like unattached EBS volumes and idle load balancers. Small savings across many resources add up to significant cost reductions over time.

Where to go next

Back to the AWS Cloud Practitioner overview.
Look up any service you could not name in the AWS services glossary.
Sit the 80-item practice exam once two or three note pages are solid.