Intermediate interview questions in DevOps & Cloud
Continuous Delivery vs Continuous Deployment: key differences and choosing between them
Tests the human-gate distinction: Delivery readies artifacts but requires manual approval; Deployment pushes automatically. Strong answers cite compliance, blast radius, and maturity. Red flag: conflating terms or claiming full automation fits every app.
Name three Linux namespaces and explain what each one isolates.
Name three of PID, Network, Mount, UTS, IPC, User, Cgroup, Time; say what each hides; cite CLONE_NEW* or /proc/pid/ns.
How do you set SLOs for a service from scratch?
Identify critical user journeys, pick SLIs that reflect user happiness, measure current performance, set achievable targets with buffer, iterate.
IaaS vs PaaS for first cloud migration
IaaS (lift-and-shift) gives control with high ops overhead; PaaS lowers ops but may need refactoring; for a monolith with limited expertise, IaaS lift-and-shift is the lower-risk first step.
How do containers enforce CPU and memory limits via cgroups?
Cover CPU CFS quota and shares, memory limits and OOM, and runtime cgroup config.
What is a build artifact and why build once deploy many crucial?
Tests whether you see artifacts as immutable deployable units. A strong answer says one binary is promoted through all stages, config is externalized, and rebuilding per environment creates drift. Red flag: accepting per-environment rebuilds.
Error budget exhausted early: what now?
Invoke the error budget policy, shift focus from features to reliability, prioritize stability work, analyze what burned the budget.
Scalability vs elasticity in the cloud
Scalability is the ability to handle more load by adding capacity; elasticity is automatically adding AND removing capacity in real time to match demand.
What does shift left mean in CI/CD, and give two concrete examples?
Your grasp of moving verification earlier to reduce cost and risk. Define shift left as earlier-stage testing; cite two concrete examples like pre-commit unit tests and PR-level SAST scans. Never call it "more testing" instead of earlier feedback.
Describe the relationship between containerd and runc in starting a container.
Tests the OCI runtime split and lifecycle ownership. A great answer states containerd handles image pull, storage, and API lifecycle, then invokes runC to spawn the isolated process.
How do you find and eliminate toil systematically?
Inventory and measure toil via time tracking or ticket analysis, prioritize by frequency times cost versus automation effort, automate highest-ROI items, measure success…
When hybrid cloud beats public or private
Give a scenario like regulated data plus bursty compute; keep sensitive data and legacy systems on-prem, run scalable or customer-facing workloads in public cloud.
What is Infrastructure as Code (IaC), and how does it support CI/CD?
This tests if you link declarative definitions to repeatable pipelines. A strong answer covers idempotence, versioned templates, and preventing snowflake environments. A red flag is calling IaC mere scripting without CI/CD integration.
Explain layered filesystems like OverlayFS and their efficiency vs monolithic models
This tests copy-on-write layering and deduplication in container storage. A strong answer covers lowerdir/upperdir/merged mounts, layer reuse across images, and why diff-based distribution beats monolithic blobs.
What makes a blameless postmortem effective?
Cover summary, impact, timeline, root cause, action items; explain blameless means focusing on systemic causes so people report honestly.
Designing an auto-scaling web tier
Front with a load balancer, define a launch template, an auto-scaling group across AZs, and target-tracking policies.
Optimize Dockerfile layer caching for npm install
Copying all source first invalidates the npm install layer on any code change; instead copy package.json and lockfile, run npm install, then copy the rest.
On-Demand vs Reserved vs Spot pricing
On-Demand for unpredictable bursty work, Reserved or Savings Plans for steady baseline, Spot for interruptible fault-tolerant jobs.
Describe Trunk-Based Development principles and CI/CD benefits
Tests if you view TBD as a CI/CD enabler versus GitFlow. Good answers name a single trunk, branches under 24 hours, pre-integrate builds, and feature flags, tying daily commits to releasable code and less merge hell. Red flag: endorsing long-lived branches.
Why use latency percentiles over the average?
Averages hide the tail and are skewed by outliers, so most users can suffer while the mean looks fine; use percentiles; prioritize p99 when tail users are high-value or fan-out…
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