Free guides, interview Q&As, and job responsibility breakdowns — curated by industry veterans to help you crack MNC interviews
Figure 2: Stopped vs. Stopped (Deallocated) — what's billed
Azure Virtual Machine (VM)
Definition: An IaaS compute resource in Azure that runs an operating system and applications, giving the administrator full control similar to a physical server.
Day-to-Day Example: Like renting a fully equipped office space — you control what happens inside it, but the building (hardware) is managed by someone else.
OS Disk
Definition: The managed disk that holds the virtual machine's operating system and boot files.
Day-to-Day Example: Like the engine and chassis of a car — the core component the whole vehicle depends on to run.
Temporary Disk
Definition: Local, short-term storage attached to a VM that is not guaranteed to persist across resizing, migration, or maintenance events.
Day-to-Day Example: Like a whiteboard in a meeting room — useful for scratch notes during the session, but wiped clean afterward.
Data Disk
Definition: An additional managed disk attached to a VM to store application data separately from the OS.
Day-to-Day Example: Like an external hard drive plugged into a laptop for extra storage, kept independent of the laptop's own drive.
Managed Disk
Definition: A VM disk type where Azure automatically creates and manages the underlying storage account, simplifying scaling and reliability.
Day-to-Day Example: Like valet parking — you hand over the car and never worry about where exactly it is stored.
Premium SSD
Definition: A high-performance, low-latency managed disk tier backed by solid-state drives, intended for production workloads.
Day-to-Day Example: Like a sports car's tires — built for speed and responsiveness under heavier demand.
VM Size (SKU)
Definition: The specific hardware configuration (vCPU, RAM, temp storage, max disks/NICs) assigned to a virtual machine.
Day-to-Day Example: Like choosing a car trim level — the same model can come in economy, standard, or performance configurations.
Stopped (Deallocated)
Definition: A VM power state in which the compute allocation is released and compute billing stops, while disk storage is still billed.
Day-to-Day Example: Like returning a rental car to the lot — you stop paying for daily use, but the parking fee for your luggage left behind still applies.
Availability Set
Definition: A logical grouping that spreads VMs across separate Fault Domains and Update Domains within one datacenter to reduce downtime from hardware failure.
Day-to-Day Example: Like splitting a company's servers across different racks in the same building so one rack failure doesn't take everything down.
Availability Zone
Definition: A physically separate datacenter with independent power, cooling, and networking, within the same Azure region.
Day-to-Day Example: Like a company having backup offices in different buildings across the same city, so one building's outage doesn't stop the whole business.
Virtual Machine Scale Set (VMSS)
Definition: A group of identical, load-balanced VMs that can automatically increase or decrease in number based on demand or a defined schedule.
Day-to-Day Example: Like a restaurant calling in extra staff during a dinner rush and sending them home once things quiet down.
Generalized Image
Definition: A VM image that has been stripped of machine-specific identity information (via Sysprep) so it can be used as a reusable template.
Day-to-Day Example: Like a blank form template — no personal details filled in yet, ready to be copied and reused many times.
Specialized Image
Definition: A VM image that retains the original VM's computer name, user accounts, and configuration, used to recreate that exact machine.
Day-to-Day Example: Like photocopying a filled-out form exactly as it is, keeping every detail already written on it.
Azure Compute Gallery
Definition: A service for storing, versioning, and sharing custom VM images across subscriptions, regions, and tenants at scale.
Day-to-Day Example: Like a company's central catalog of approved equipment models, available to every branch office that needs to order one.
Azure Spot VM
Definition: A VM purchasing option that uses Azure's spare capacity at a steep discount, with the risk of eviction when that capacity is reclaimed.
Day-to-Day Example: Like buying a standby airline ticket — much cheaper, but you might get bumped if a full-fare passenger needs the seat.
Azure Hybrid Benefit
Definition: A licensing benefit that lets customers apply existing on-premises Windows Server or SQL Server licenses toward Azure VM costs.
Day-to-Day Example: Like transferring a gym membership you already paid for to a new branch instead of buying a second one.
Boot Diagnostics
Definition: A VM feature that captures a screenshot and serial log of the boot process to help diagnose startup failures.
Day-to-Day Example: Like a dashcam recording a car's ignition sequence, so a mechanic can see exactly what happened if it won't start.
VM Extension
Definition: A small software package deployed onto a VM after creation to perform configuration, monitoring, or automation tasks.
Day-to-Day Example: Like an app you install on a new phone after setup, adding a specific feature it didn't come with out of the box.
Proximity Placement Group
Definition: A grouping construct that ensures Azure places VMs as physically close together as possible to minimize network latency.
Day-to-Day Example: Like seating an entire project team at the same table so they don't waste time walking across the building to talk.
Azure Bastion
Definition: A fully managed service that provides secure RDP/SSH connectivity to VMs through the Azure portal, without exposing a public IP address.
Day-to-Day Example: Like a hotel's front desk that lets a verified guest into their room without ever handing out a key that works on the street door.
Figure 3: Azure Managed Disk Tiers — Cheat Sheet
Figure 4: Availability Set vs. Availability Zone vs. VM Scale Set
1. Stopped vs. Stopped (Deallocated)
Feature Stopped (via OS shutdown) Stopped (Deallocated) Compute billing Still charged Not charged Hardware allocation Reserved for the VM Released back to Azure Dynamic Public IP Retained May be released
2. Availability Set vs. Availability Zone
Feature Availability Set Availability Zone Scope of protection Within one datacenter Across separate datacenters Mechanism Fault Domains & Update Domains Physically isolated zones in a region Common confusion Mistaken as protecting against a full datacenter outage It protects at a broader, datacenter-level scope
3. Managed Disk vs. Unmanaged Disk
Feature Managed Disk Unmanaged Disk Storage account handling Fully managed by Azure Customer manages the storage account Scaling risk No IOPS throttling limits from a shared account Risk of hitting storage account IOPS limits Recommended use Default choice for virtually all VMs Legacy scenarios only
4. Standard SSD vs. Premium SSD
Feature Standard SSD Premium SSD Performance Moderate, consistent latency High IOPS, low latency Best suited for Web servers, dev/test workloads Production databases and I/O-heavy apps Cost Lower Higher
5. Generalized Image vs. Specialized Image
Feature Generalized Image Specialized Image Identity information Removed via Sysprep Retained from the source VM Typical use Template for creating many new VMs Recreating or restoring one specific VM Common confusion Assumed to keep the original computer name It is generalized images that strip that identity
6. Availability Set vs. Virtual Machine Scale Set
Feature Availability Set VM Scale Set Purpose Spreads fixed VMs for fault tolerance Automatically scales VM instance count Instance count Fixed, manually managed Elastic — grows/shrinks with demand Example use A pair of domain controllers A web tier handling variable traffic
7. Pay-As-You-Go VM vs. Azure Spot VM
Feature Pay-As-You-Go VM Azure Spot VM Price Standard on-demand rate Deeply discounted Eviction risk None Can be evicted with little notice Best suited for Production, always-on workloads Batch jobs, dev/test, interruptible tasks
8. OS Disk vs. Temporary Disk vs. Data Disk
Disk Type Best Suited For OS Disk Hosting the operating system and boot files Temporary Disk Short-term scratch/page-file data that can be lost Data Disk Persistent application and business data
9. Public IP + RDP/SSH vs. Azure Bastion
Feature Public IP + Direct RDP/SSH Azure Bastion Public IP exposure Required on the VM Not required on the VM Attack surface Higher — port open to the internet Lower — access brokered through the portal Access path Direct client-to-VM connection Browser-based session via Azure portal
10. Managed Disk Tiers Compared
Tier Performance Level Typical Use Standard HDD Lowest Backup, infrequently accessed data Standard SSD Balanced Web servers, dev/test Premium SSD High Production workloads Ultra Disk Highest SAP HANA and top-tier databases
Q1. What is an Azure Virtual Machine, and what three components make it up?
Answer: An Azure Virtual Machine is an IaaS compute resource offering full OS control; it is made up of Compute (vCPU + RAM), Storage (disks), and Networking (NIC + Virtual Network).
Q2. What is the difference between the OS Disk and the Temporary Disk?
Answer: The OS Disk stores the operating system and boot files and persists durably, while the Temporary Disk provides short-term local storage that is not guaranteed to survive resizing or migration.
Q3. Why are Managed Disks recommended over Unmanaged Disks?
Answer: Managed Disks let Azure handle the underlying storage account automatically, removing the risk of hitting shared storage account IOPS limits and simplifying scaling and reliability.
Q4. What factors does the VM Size (SKU) determine?
Answer: VM Size determines the number of vCPUs, the amount of RAM, temporary storage capacity, and the maximum number of data disks and network interfaces the VM can support.
Q5. What is the difference between Stopping and Deallocating a VM?
Answer: Stopping a VM from the guest OS still reserves the underlying hardware and continues compute billing, while Deallocating releases that hardware allocation and stops compute charges.
Q6. What is an Availability Set, and what does it protect against?
Answer: An Availability Set spreads VMs across Fault Domains and Update Domains within a single datacenter, protecting against hardware failure and planned maintenance within that datacenter.
Q7. What is an Availability Zone, and how does its scope differ from an Availability Set?
Answer: An Availability Zone is a physically separate datacenter within the same region; unlike an Availability Set, it protects against a full datacenter-level outage, not just a single rack or host failure.
Q8. What is a Virtual Machine Scale Set used for?
Answer: A VM Scale Set automatically adds or removes identical VM instances to match demand, enabling horizontal scaling for workloads with variable traffic.
Q9. What is the difference between a Generalized and a Specialized VM image?
Answer: A Generalized image has had machine-specific identity removed via Sysprep and is used as a reusable template, while a Specialized image retains the original VM's identity and is used to recreate that exact machine.
Q10. What is Azure Compute Gallery used for?
Answer: Azure Compute Gallery is used to store, version, and share custom VM images across subscriptions, regions, and tenants at scale.
Q11. What is an Azure Spot VM, and what is the trade-off?
Answer: An Azure Spot VM uses Azure's spare capacity at a steep discount; the trade-off is that it can be evicted with little or no notice when Azure needs that capacity back.
Q12. What is Azure Hybrid Benefit, and how does it reduce cost?
Answer: Azure Hybrid Benefit lets customers apply existing on-premises Windows Server or SQL Server licenses to Azure VMs, reducing or eliminating the licensing portion of the VM cost.
Q13. What does Boot Diagnostics help troubleshoot?
Answer: Boot Diagnostics captures a screenshot and serial console log of the boot process, helping administrators diagnose a VM that fails to start or hangs during boot.
Q14. What is a VM Extension, and give an example.
Answer: A VM Extension is a small software package deployed after VM creation to perform configuration or automation; the Custom Script Extension, which runs a script on the VM, is a common example.
Q15. What is the purpose of Azure Bastion?
Answer: Azure Bastion provides secure RDP/SSH access to VMs directly through the Azure portal, removing the need to expose a public IP or open management ports to the internet.
Q1. A company needs to guarantee that compute billing stops completely while a VM is not in use. What should they do?
Answer: They should shut the VM down through the Azure portal/CLI so it reaches the Stopped (Deallocated) state, rather than only shutting down the guest OS, which still reserves hardware and continues billing.
Q2. A company wants to protect a two-tier application's VMs from a single rack or host hardware failure within one datacenter. What should they configure?
Answer: They should place the VMs in an Availability Set, which spreads them across separate Fault Domains and Update Domains within that datacenter.
Q3. A company wants resiliency against an entire datacenter failure within the same region. What should they use?
Answer: They should deploy their VMs across Availability Zones, which places them in physically separate datacenters within the same region.
Q4. An e-commerce site needs to automatically add or remove VM instances based on changing traffic levels. What should be deployed?
Answer: They should deploy a Virtual Machine Scale Set (VMSS), which automatically scales the number of identical VM instances up or down based on demand.
Q5. An administrator wants to create a reusable template VM image with no leftover identity information for mass deployment. What type of image should they create, and what must be done first?
Answer: They should create a Generalized image; the source VM must first be prepared with Sysprep to remove machine-specific identity information before capturing the image.
Q6. A finance team wants to run large batch-processing jobs at the lowest possible cost and can tolerate the job being interrupted. What VM purchasing option fits?
Answer: They should use Azure Spot VMs, which offer significant discounts on unused Azure capacity in exchange for the risk of eviction.
Q7. A company already owns Windows Server licenses on-premises and wants to reduce the licensing cost of its Azure VMs. What should they use?
Answer: They should apply Azure Hybrid Benefit, which lets them use their existing on-premises Windows Server licenses to lower Azure VM licensing costs.
Q8. A security team wants to eliminate public IP exposure on a VM's RDP port while still allowing occasional remote access from the Azure portal. What should they implement?
Answer: They should implement Azure Bastion, which provides secure, browser-based RDP/SSH access through the Azure portal without requiring a public IP on the VM.
