Cloud primer

Public cloud services are available through a number of cloud service models. These models impact the way you buy, use and manage a service. In many cases, you can combine services based on different models into a single solution. This flexibility is one of the core benefits of using public cloud services.

Software-as-a-Service (SaaS)

Software-as-a-Service offerings are software-based services you buy through a subscription and consume with minimal configuration. The service provider manages the entire service stack, and your organisation bears no responsibility for hosting or maintaining the underlying platform (hardware or software).

Common Software-as-a-Service use cases are:

• migrating your on-premises email to Microsoft Office 365

• using SalesForce as a web-based Customer Relationship Management (CRM) capability

The Cloud Service Provider (CSP) must deliver the service to stated service level agreements (SLA), and will ensure it is secure, performant and continuously updated.

Platform-as-a-Service (PaaS)

Platform-as-a-Service offerings allow development teams to focus on developing and deploying applications, and not on managing infrastructure - such as servers and operating systems. Most elements of the technical stack are managed by the provider.

Common Platform-as-a-Serivce use case is:

• migrating your application's database to Google CloudSQL from an on-premises database server

• deploying an application to run on Amazon Web Services (AWS) using Elastic Beanstalk - a service that automatically provisions and manages the underlying requirements of your application

PaaS offerings are generally standardised and do not offer the same flexibility as a traditional server-based hosting environment.

Infrastructure-as-a-Service (IaaS)

Infrastructure-as-a-Service offerings allow you to provision virtual infrastructure components within public cloud environments - such as servers, storage and networks. The cloud provider owns, maintains and operates the physical elements of the technical stack – network, storage and server hardware. Your organisation deploys, maintains and operates the virtual infrastructure on top. This is similar to how you might operate in your existing datacentre, but with IaaS you bear no responsibility for maintaining the underlying hardware estate, or the datacentre itself.

Common Infrastructure-as-a-Serivce use case is:

• migrating an application from a server in your datacentre to an AWS virtual server instance or Azure virtual machine

Function-as-a-Service (FaaS)

Function-as-a-Service offerings, also known as Serverless, is another way of deploying applications within a public cloud environment. Using FaaS allows you to break your application code into discrete functions that are executed on-demand and without the need to provision or maintain servers.

The benefit of FaaS is that you only pay for what you use (when your code is running) and the service scales to meet demand. If the function is in high demand, the cloud services automatically scales to meet it. If the demand ceases, your application scales down accordingly and you stop incurring costs.

Common examples of Function-as-a-Service are:

• AWS Lambda, Azure Functions and Google Cloud Functions