Cloud Computing Fundamentals
Cloud Computing Fundamentals tests the vocabulary and operating model of public and private cloud: service models, the shared responsibility model, regions and availability zones, elasticity, and storage and network primitives.
Service models
IaaS supplies virtual machines, block storage, and networks; you manage the guest OS and above. PaaS supplies a runtime and managed services; you manage your application and data. SaaS supplies a finished application. The higher the abstraction, the less you patch, but the less you control.
Shared responsibility
The provider secures the physical facilities, hypervisor, and managed service infrastructure. In IaaS the customer still patches the guest OS, configures security groups, and manages identity and data. Responsibility moves upward with PaaS and SaaS but never disappears: data classification, access policy, and account configuration remain yours.
Regions, zones, and elasticity
A region is a geographic area; availability zones are isolated data centers within it. Deploying across zones improves resilience, not latency between distant regions. Elasticity means adding or removing capacity automatically; scalability means the system can handle growth, whether or not that is automatic. Object storage is for unstructured objects accessed by API; block storage is a disk attached to one instance.
Worked example: a team runs its own database on a cloud VM and asks who patches the database engine. Because this is IaaS, the team does. The provider patches the hypervisor and physical host, but the guest OS and database are the customer's responsibility.
Traps: assuming the provider secures everything; confusing an availability zone with a region; treating object storage as a mounted filesystem for a database; and ignoring egress charges, which apply to data leaving the provider network.