Cloud Computing

High availability - services experience verry little downetime when using the cloud. should have 99.999% availability or 5 mins and 15 secs of downtime per year. to do this have to have reliable systems that are highly available. atleast two webservers.

scalability - Ability to increase the numver of people or systems. linear sacal vs expotential scale. Facebook, google, linkedin, you can just go to amazon and use some of their compute power.

Vertical scale - you can scale up the processors ram storage bandwidth on one machine.

horizintal scale. additional resources, instead of one larger compute go from one to two.

Rapid elasticity - you use virtualization so only using portions or all at a time. Elaciticy is the sysems

Metered utiization - being charged for a service on a pay per use , number of users, number of connections, number of stored data.

AWL lambda for every 1 million requests it’s about 20 cents.

Measured - is the ability to pay for something on a concumption service. you pay a monthly fee for a certan amount of usage oncce you hit the limit your service may stop or you pay an additional amount. old school data plans.

cloud is mostly metered.

Shared resources - ability to minimize costs by putting VMs on someone elses servers. Divding an expensive server for virtual machinees for shared use is more efficnet.

File Synchronization - ability to store data whic can then spread to other places depending on configuration.

Cloud Concepts – Exam Essentials

High availability (HA)

Goal: Very little downtime.
“Five Nines” (99.999%) → ~5 min 15 sec downtime/year.
Achieved by redundancy (e.g., at least 2 web servers, load balancers, failover systems).

Scalability

Ability to grow capacity as demand increases.
Vertical Scaling (Scale Up): Add CPU, RAM, storage to one server.
Horizontal Scaling (Scale Out): Add more servers (e.g., 1 → 2 → 10).
Linear vs Exponential: Small apps grow linearly; big platforms (Google, FB) scale horizontally using cloud compute.

Rapid Elasticity

Resources can expand or shrink quickly based on demand.
Enabled by virtualization.
Example: AWS auto-scales web servers during traffic spikes.

Metered / Measured Utilization

Pay-per-use model (like electricity).
You are billed for CPU hours, storage used, requests, bandwidth, or users.
Example: AWS Lambda ≈ $0.20 per 1M requests.
Old analogy: cell phone “minutes” or data plan caps.

Resource Pooling / Shared Resources

Providers pool hardware (multi-tenancy).
One large server runs many virtual machines (VMs) for different customers.
Increases efficiency, lowers cost.

File Synchronization

Cloud keeps files consistent across devices/locations.
Examples: OneDrive, Google Drive, Dropbox.
Data replicated across multiple servers or regions for availability and convenience.

✅ Exam Must-Knows

High availability = redundancy + failover.
Scalability: Vertical = bigger box; Horizontal = more boxes.
Elasticity = automatic scaling up/down.
Metered use = pay only for what you consume.
Resource pooling = multi-tenant efficiency.

⚡Memory Trick:

Think SHaRe-M for cloud features:

Scalability
High availability
Rapid elasticity
Metered use