DevOps & Cloud interview questions

Ansible is an open-source automation tool that configures servers and deploys applications by running YAML playbooks over SSH, with no agent on the machines.

No. Ansible is agentless: it connects from a control machine over SSH (or WinRM on Windows) and runs its modules there, needing only Python on the managed hosts.

A YAML file that lists plays, each mapping a group of hosts to a series of tasks, such as installing packages, copying files and restarting services.

That running the same task twice has the same result as running it once. A module that installs a package does nothing if the package is already installed.

Autoscaling is the automatic adding or removing of computing resources, such as servers or containers, based on demand to keep performance steady and costs low.

Horizontal scaling adds more machines or containers that share the work, while vertical scaling gives a single machine more CPU, memory, or storage. Autoscaling usually means horizontal scaling because it can happen without downtime.

It can, because you pay for extra capacity only while you need it instead of sizing for the peak all day. Poorly tuned limits or scaling on the wrong metric can still waste money or leave the app short on capacity.

Scale to zero means removing every instance when there is no traffic, so an idle app costs almost nothing. It is common on serverless platforms, with the trade-off of a cold start delay when the next request arrives.

AWS (Amazon Web Services) is Amazon's cloud platform: more than 200 pay-as-you-go services for servers, storage, databases and much more.

EC2 rents virtual servers that run your software. S3 stores files, called objects, in buckets and serves them over HTTP. Many applications use both.

AWS has a free tier with limited usage of many services, mainly for learning and small projects. Beyond that, you pay for what you use, such as server hours, storage and data transfer.

A geographic area, such as Frankfurt or Ireland, where AWS runs several separate data centers called availability zones. You choose a region for each resource, usually close to your users.

Microsoft Azure is Microsoft's cloud computing platform, offering hundreds of on-demand services such as virtual machines, databases and AI models worldwide.

Both offer a similar range of cloud services. AWS is the largest and oldest provider with the broadest catalog; Azure integrates most closely with Microsoft tools, identity and enterprise agreements. The choice often follows a company's existing technology and contracts.

A container that holds related resources, such as a web app, its database and storage, so they can be managed, secured, billed and deleted together.

Yes. New accounts get credit for the first month, and many services include an always-free monthly amount, such as a small number of function executions or a basic database tier.

Blue-green deployment is a release strategy that uses two identical production environments and moves all traffic from the old version to the new one at once.

Blue-green deployment moves all traffic from the old version to the new one in a single switch. A canary deployment sends a small share of traffic to the new version first and increases it gradually while watching error rates and performance.

Both environments usually share one database, so schema changes must be backward compatible with the old version. A common approach is expand and contract: first add new columns or tables without removing anything, deploy the new code, and remove old structures only in a later release.

It can, because two full production environments run at the same time during a release. With cloud infrastructure and containers, the idle environment can be created just before a release and removed afterward to limit the extra cost.

A canary deployment releases a new software version to a small share of users first, checks its health, and then gradually rolls it out to everyone.

Blue-green deployment switches all traffic from the old environment to the new one in a single step, while a canary deployment moves traffic gradually, starting with a small percentage. Canaries limit how many users see a bug, while blue-green makes the switch and the rollback simple and instant.

Teams often start with 1% to 10% of traffic, then increase in steps such as 25%, 50%, and 100%. The right starting point depends on how much traffic you have, since the canary needs enough requests to produce meaningful metrics.

It is named after the canaries coal miners carried to detect dangerous gas early. The small group of users who get the new version first acts as an early warning for problems.

A CDN is a network of servers spread around the world that stores copies of website content and delivers it to each user from the nearest location.

A CDN helps most when your visitors are spread across different regions or your site serves many images, scripts, or videos. Many hosting platforms include a CDN automatically, so you may already be using one.

Web hosting stores your site and runs its application code on an origin server. A CDN sits in front of that server and delivers cached copies of the content from locations close to your users.

A cache hit means the CDN edge server already had a stored copy of the requested file and served it directly. A cache miss means it had to fetch the file from the origin server first.

Chaos engineering is the practice of deliberately injecting failures into a system, such as crashing servers, to confirm that it keeps working as expected.

Mature teams do run experiments in production, because only production has real traffic and real configurations. They start in test environments, limit the blast radius to a small share of users or servers, and stop automatically if key metrics degrade.

A test checks a known condition and either passes or fails. Chaos engineering is an experiment that explores how a complex system behaves when something breaks, and it often reveals problems nobody thought to write a test for.

A game day is a planned session where a team deliberately causes failures, such as shutting down a whole availability zone, and practices detecting and recovering from them. It tests both the system and the team's incident response.