More in DevOps & Cloud — page 23
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.
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 containers enforce CPU and memory limits via cgroups?
WHAT IT TESTS: Knowledge that cgroups enforce limits in the kernel, not Docker. ANSWER OUTLINE: Cover CPU CFS quota and shares, memory limits and OOM, and runtime cgroup config. RED FLAG: Confusing cgroups with namespaces or saying Docker throttles.
Name three Linux namespaces and explain what each one isolates.
WHAT IT TESTS: Kernel primitives behind container isolation. ANSWER OUTLINE: Name three of PID, Network, Mount, UTS, IPC, User, Cgroup, Time; say what each hides; cite CLONE_NEW* or /proc/pid/ns.
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.
Docker Content Trust: Signed Image Verification
Docker Content Trust is a cryptographic tamper-evident seal for image tags. It lets you verify who published an image before pulling from any registry. The footgun is that without DOCKER_CONTENT_TRUST=1, unsigned tags pull silently with no warning.
Container Images Are Stacked Deltas
Images stack read-only layers like transparent sheets, one per Dockerfile step, topped by a thin writable layer. This enables cache reuse and fast pulls. The footgun: removing a file in a later layer hides but does not delete it; those bytes still ship.
OLM: Kubernetes' App Store for Operators
OLM is the app store for Kubernetes Operators: it installs, updates, and resolves dependencies declaratively. Use it when managing third-party or custom Operators across clusters.
ResourceQuota: Namespace Resource Budgets
ResourceQuota is a namespace budget: it rejects pods once total requests hit the cap. Use it to keep multi-tenant clusters fair. The footgun: it counts requested resources, not real usage, and pods missing requests may be rejected without LimitRange defaults.
ConfigMap decouples config from container images
A ConfigMap is a key-value store that injects configuration into pods without rebuilding the image. Use it for feature flags, database hostnames, or any non-secret settings. Editing one does not restart existing pods, so stale config is the common footgun.
EndpointSlice: Splitting the Monolithic Endpoints List
EndpointSlice shards a service's pod backends into smaller chunks instead of one massive list. This keeps kube-proxy and DNS fast when services scale to thousands of pods. Do not edit them by hand; the controller owns them and will overwrite your changes.
Pod QoS Classes: Guaranteed, Burstable, BestEffort
Kubernetes QoS classes are eviction priorities, not performance guarantees. Under node pressure, the kubelet kills BestEffort pods first, then Burstable, then Guaranteed. Omitting limits does not grant infinite headroom; it makes your pod die first.
OCI: The USB-C of Containers
OCI is the USB-C of containers: open standards that let any compliant runtime execute any image. It prevents vendor lock-in by decoupling image format from runtime. The footgun is treating "Docker image" as proprietary rather than an OCI-compliant bundle.
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.
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.
Kappa Architecture Unifies Batch and Stream
Kappa treats batch as a special case of streaming: store every event in an immutable log, compute views in real time, and replay the log when logic changes. It removes Lambda's dual codebase but forces you to pay for infinite retention and replay costs.
AWS Cost and Usage Report (CUR)
Think of CUR as your AWS itemized receipt, delivered daily to S3. It breaks down charges by hour, product, resource, and tag for spreadsheets or Athena queries. Mid-month numbers are estimates, so do not lock budgets until the report finalizes after invoicing.
CloudEvents: The Event Data Standard
CloudEvents provides a common envelope for event data, enabling routing without custom parsers. Use it when events cross clouds, SaaS tools, or internal services. It standardizes wrappers, not payloads, so producers and consumers still need aligned schemas.
AWS SDK: Code That Operates Your Cloud
The AWS SDK turns AWS API calls into native code so your app can command S3 or DynamoDB directly. It handles auth, retries, and formatting automatically. The footgun: forgetting region or credentials causes silent failures that look like network errors.
IAM: The Gatekeeper Framework
IAM is the framework that decides who gets through the door and what they can touch inside your systems. It governs every employee transition, from onboarding to departure. The trap is treating IAM as a one-time setup rather than an ongoing lifecycle process.