Easy interview questions in DevOps & Cloud
What defines toil, with an example?
Define toil as manual, repetitive, automatable, tactical, no-enduring-value, scaling-with-growth work; distinguish it from overhead; give a concrete example.
What is a container vs a VM?
Containers share the host kernel and isolate via namespaces and cgroups; VMs run a full guest OS on a hypervisor; containers are lighter and faster.
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.
What is CI, and what is its single most important goal?
Frequent merges to a shared branch with automated build and test; top goal is a workable integrated codebase.
SLI vs SLO vs SLA: how do they relate?
SLI is a measured metric, SLO is the internal target for that metric, SLA is the external contract with consequences.
How do Docker images and containers differ and relate?
This tests your grasp of the immutable template versus mutable runtime boundary. A good answer: an image is a read-only layered template with code and dependencies; a container is a runnable instance with a writable layer on top.
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.
Describe the typical CI pipeline sequence from push to deploy
This tests stage ordering and failure handling. A strong answer lists build, test, and deploy stages; notes intra-stage parallelism and inter-stage sequencing; and mentions early termination on failure.
How do SRE and DevOps relate?
DevOps is a broad culture of breaking down silos; SRE is one prescriptive way to do it with specific practices.
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.
Build, tag, and run a container with port mapping
Docker build -t my-app:1.0 . to build and tag; docker run -d -p 8080:80 my-app:1.0 to run detached with host:container port mapping.
Launching a virtual machine in the cloud
Pick image, instance type, network placement and security, attached storage, and access keys.
Dockerfile COPY versus ADD
COPY just copies local files; ADD also auto-extracts local tarballs and can fetch remote URLs; prefer COPY for predictability, use ADD for local archive extraction.
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.
Difference between git merge and git rebase before a pull request
Rebase rewrites SHAs, duplicating CI builds; merge keeps identity and triggers one build.
Explain the three pillars of observability
Metrics are cheap aggregated time series for detecting and alerting, logs are discrete event records for detail and context, traces follow one request across services to localize latency.
Dockerfile CMD versus ENTRYPOINT
ENTRYPOINT sets the fixed executable; CMD sets default args or the default command; run-time args override CMD but append to ENTRYPOINT. Use together to make a fixed binary with overridable defaults.
Describe using a pre-push Git hook for checks and its CI limitations.
It tests client-side automation versus server-side policy. An executable .git/hooks/pre-push script runs tests and exits non-zero to block, noting hooks are not cloned, skipped via --no-verify, and local-only. A red flag is treating them as policy gate.
What are the Four Golden Signals?
Name latency, traffic, errors, and saturation; explain each briefly; describe measuring latency as a distribution separating success from failure.
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.
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