Easy interview questions in Cloud Platforms
Explain the difference between IaaS, PaaS, and SaaS with examples
This tests your grasp of cloud abstraction layers and shared responsibility. A strong answer maps IaaS to raw infrastructure like EC2, PaaS to managed runtimes like Heroku, and SaaS to end-user apps like Gmail.
How does shared responsibility shift between IaaS and SaaS?
Tests your understanding of security ownership across cloud stacks. Strong answer: in IaaS you own OS, apps, and network controls; in SaaS you only own data, identities, endpoints, and accounts while the provider manages the rest.
CapEx vs OpEx in cloud migration
CapEx is large upfront asset spend, OpEx is ongoing pay-as-you-go cost; cloud shifts spending from CapEx to OpEx, trading ownership for flexibility.
Launching a virtual machine in the cloud
Pick image, instance type, network placement and security, attached storage, and access keys.
What a machine image is and why it matters
An image is a frozen template of OS, software, and config; it makes launches identical and fast.
Object vs block vs file storage
Object stores flat keyed blobs over HTTP, block gives raw volumes for one VM, file offers a shared hierarchical mount.
Serving user images securely from object storage
Store images in a private bucket, serve via a CDN with origin access control, use signed URLs for private content.
Public and private subnet VPC design
Web server in a public subnet routed to an internet gateway, database in a private subnet with no inbound from the internet, NAT for outbound.
Layer 4 vs Layer 7 load balancers
L4 routes on IP and TCP/UDP ports fast and protocol-blind; L7 inspects HTTP for host, path, and headers.
How cloud DNS resolves a URL to an IP
Recursive resolver queries root, then TLD, then your authoritative cloud DNS zone; the matching record returns an IP, cached per TTL.
IAM Role vs IAM User
A user is a fixed identity with long-lived credentials for a person; a role is assumable with temporary credentials for workloads or cross-account access.
Security Groups vs NACLs
A security group is stateful and attached to instances or NICs; a NACL is stateless and applied at the subnet.
Choosing relational vs NoSQL managed databases
Choose relational for complex relationships, joins, flexible queries, and strong transactions; choose NoSQL for known access patterns needing massive horizontal scale.
Read replicas in managed relational databases
A read replica is an async copy of the primary that serves read-only queries, offloading the primary and scaling read-heavy workloads; expect replication lag.
How does caching reduce database load?
Cache-aside reads, RAM-speed lookups, TTL plus invalidation.
The cloud shared responsibility model
The provider secures the cloud (hardware, OS, runtime), you secure what runs in it (code, data, config, access).
Why not store uploads on local PaaS disk?
PaaS instances are ephemeral and unshared, so local files vanish on restart and are invisible to peers; store uploads in object storage.
Deploying to Heroku via Git
Push to the remote, a buildpack detects the language, builds a slug, and runs the Procfile process.
Writing a Dockerfile for a web app
FROM a base, set WORKDIR, install dependencies before app code for cache reuse, EXPOSE the port, CMD the start command.
Kubernetes Deployment versus Pod
A Pod is the smallest disposable unit, a Deployment maintains a desired replica count, self-heals, and rolls out updates.
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