Fundamental
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Fundamental
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PaaS Splits OS Patching and App Control
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An organization is planning to migrate an internal line-of-business web application to Azure. The IT management team establishes the following operational requirements:
- The cloud provider must manage physical hardware, virtualization, operating system installation, and security patching.
- The internal IT team will not be responsible for underlying runtime environment updates.
- The development team must retain full control over the deployment, code, and configuration of the custom web application and its data.
Which cloud service model should the organization choose to minimize operational overhead while fulfilling these requirements?
Explanations
Infrastructure as a Service (IaaS)
Infrastructure as a Service (IaaS)
What Infrastructure as a Service (IaaS) Is
Infrastructure as a Service (IaaS) is a cloud computing model where the cloud service provider delivers fundamental computing, storage, and networking resources on demand over the internet. In an IaaS model, the customer rents virtual machines (VMs) and networking infrastructure.
Why It Doesn't Meet the Requirement
While IaaS removes the burden of managing physical data centers and hardware, it introduces substantial operational overhead for the customer:
- OS patching: The customer is directly responsible for installing, configuring, securing, and patching the guest operating system.
- Runtime maintenance: Middleware, web servers (such as IIS or Apache), and runtime frameworks (such as .NET or Java) must be installed and patched by the customer.
- Security configurations: The customer must configure host-level firewalls, antivirus definitions, and backup agents.
Key Characteristics and Limitations
- Maximum cloud control: Provides root or administrative access to the underlying virtual machine.
- High maintenance burden: Requires dedicated sysadmin personnel to manage OS-level operational lifecycles.
- Flexible environment: Allows installation of legacy software and specialized operating system customizations.
This Answer Would Be Correct If
This option would be correct if the organization required custom kernel modifications, legacy OS versions unsupported by managed platforms, or administrative access to the underlying operating system environment.
Additional Context
In the shared responsibility model, IaaS provides the highest level of customer control among cloud models, but this control comes with the trade-off of higher day-to-day administrative and maintenance effort.
On-premises private cloud
On-premises private cloud
What an On-Premises Private Cloud Is
An on-premises private cloud is a computing deployment located within an organization's own data center, where all computing, networking, and storage resources are dedicated exclusively to that single enterprise.
Why It Doesn't Meet the Requirement
An on-premises deployment represents the highest possible level of operational overhead because the customer assumes 100% of the responsibility across all layers of the technology stack:
- Physical facility management: The organization must manage real estate, physical security, cooling, power, and rack space.
- Hardware lifecycle: Server provisioning, storage array configuration, network switches, and hardware failures must be handled by in-house technicians.
- Full software stack: The customer must manage the hypervisor, operating system installation, continuous security patching, and middleware runtimes.
Key Characteristics and Limitations
- Total responsibility: No operational tasks are offloaded to a third-party cloud provider.
- High capital expenditures (CapEx): Requires substantial upfront investment in hardware and facilities.
- Complex maintenance: Requires specialized engineering teams to maintain physical infrastructure, virtualization layers, and disaster recovery.
This Answer Would Be Correct If
The organization had strict regulatory mandates requiring physical custody of hardware, lacked internet connectivity, or chose not to migrate any workloads to a public cloud provider.
Additional Context
The shared responsibility model does not apply to traditional on-premises infrastructure because no responsibilities are shared; the customer owns every operational and security domain from physical security up to data governance.
Software as a Service (SaaS)
Software as a Service (SaaS)
What Software as a Service (SaaS) Is
Software as a Service (SaaS) delivers complete, fully functional software applications over the internet on a subscription basis. Examples include Microsoft 365, Salesforce, and Dynamics 365, where end users interact directly with ready-to-use software.
Why It Doesn't Meet the Requirement
In a SaaS solution, the service provider manages almost the entire technology stack, leaving very little technical control to the customer:
- Custom code hosting: SaaS does not provide a hosting platform for deploying internal, custom-developed line-of-business applications.
- Limited customization: Customers can only configure application settings and access policies; they cannot deploy arbitrary source code or control the hosting runtime.
- Application development scope: SaaS is intended for consuming pre-built commercial software rather than building custom systems.
Key Characteristics and Limitations
- Minimal operational overhead: The vendor manages infrastructure, operating systems, application code, databases, and updates.
- Subscription consumption: Software is delivered as a turnkey service accessible via web browsers or client apps.
- End-user focus: Primarily addresses business productivity needs rather than custom software hosting.
This Answer Would Be Correct If
The organization wanted to replace an in-house tool entirely with an off-the-shelf, vendor-managed application (such as adopting an existing enterprise email or CRM solution) without writing or deploying custom code.
Additional Context
While SaaS minimizes administrative overhead more than any other cloud model, it shifts the responsibility of application logic and source code entirely to the vendor, preventing custom application hosting.
Platform as a Service (PaaS)
Platform as a Service (PaaS)
What Platform as a Service (PaaS) Is
Platform as a Service (PaaS) provides a complete cloud environment that includes infrastructure, operating systems, development tools, database management systems, and business analytics. In a PaaS deployment, the cloud provider manages the underlying infrastructure and software stack, enabling developers to focus exclusively on creating, testing, and deploying custom software.
How It Meets the Requirements
Under the shared responsibility model, PaaS transfers the operational overhead of the physical environment, operating system maintenance, and runtime framework patching to the cloud provider:
- Operating system and runtime patching: The provider automates OS updates, security fixes, and middleware maintenance without requiring customer intervention.
- Physical infrastructure: The provider handles all data center facilities, server hardware, and virtualization hypervisors.
- Application and data control: The organization retains complete ownership and management responsibility for deploying the application code, managing data assets, and setting application configurations.
Key Advantages and Capabilities
- Reduced operational burden: Eliminates time spent on routine server maintenance, allowing IT teams to focus on innovation.
- Built-in scalability: Allows rapid scaling of compute and memory resources based on traffic demands.
- Integrated developer tools: Provides native support for CI/CD pipelines, container orchestration, and automated deployments.
- High availability by default: Includes platform-level redundancy and automated recovery mechanisms.
Why This Is Optimal
PaaS delivers the ideal operational balance for this scenario. It eliminates lower-level operational duties such as OS patching and runtime maintenance (which would be required in IaaS) while still providing the development team with the necessary control to host and configure their own custom code (which is not possible in SaaS).
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