DevOps-Interview: docs: Add essential core-concepts DevOps interview questions and answers

Signed-off-by: NotHarshhaa <[email protected]>

Author: NotHarshhaa

core-concepts/README.md

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+# **Core Concepts - DevOps Fundamentals**  
+
+## **Beginner Level (1-20 Questions)**  
+
+### **1. What is DevOps?**  
+
+**Answer:** DevOps is a set of practices that combine software development (Dev) and IT operations (Ops) to improve collaboration, automate workflows, and accelerate software delivery.  
+
+### **2. What are the main goals of DevOps?**  
+
+**Answer:**  
+
+- Faster delivery of software  
+- Improved collaboration between teams  
+- Automation of repetitive tasks  
+- Continuous feedback and improvement  
+
+### **3. What are the key components of DevOps?**  
+
+**Answer:**  
+
+- **CI/CD** (Continuous Integration/Continuous Deployment)  
+- **Infrastructure as Code (IaC)**  
+- **Monitoring and Logging**  
+- **Collaboration and Communication**  
+
+### **4. How does DevOps differ from traditional IT operations?**  
+
+**Answer:** DevOps focuses on automation, collaboration, and continuous feedback, whereas traditional IT operations follow a siloed approach with manual deployments and slow release cycles.  
+
+### **5. What is Continuous Integration (CI)?**  
+
+**Answer:** CI is a practice where developers frequently integrate code into a shared repository, followed by automated testing to detect errors early.  
+
+### **6. What is Continuous Deployment (CD)?**  
+
+**Answer:** CD is the automated release of validated code changes into production, ensuring rapid and reliable delivery.  
+
+### **7. What is Infrastructure as Code (IaC)?**  
+
+**Answer:** IaC is managing infrastructure using code, enabling automation, consistency, and easy scalability. Examples: Terraform, CloudFormation.  
+
+### **8. What is version control, and why is it important?**  
+
+**Answer:** Version control tracks code changes, enabling collaboration and rollback. Example: Git.  
+
+### **9. What are some popular version control tools?**  
+
+**Answer:** Git, GitHub, GitLab, Bitbucket, Subversion (SVN).  
+
+### **10. What is a DevOps pipeline?**  
+
+**Answer:** A DevOps pipeline automates software delivery using stages like build, test, deploy, and monitor.  
+
+### **11. What is containerization?**  
+
+**Answer:** Containerization packages applications with dependencies, making them portable and consistent across environments. Example: Docker.  
+
+### **12. What are microservices?**  
+
+**Answer:** Microservices are small, independent services that communicate via APIs, improving scalability and maintainability.  
+
+### **13. What is a monolithic vs. microservices architecture?**  
+
+**Answer:** Monolithic apps have a single codebase; microservices break the application into independent, loosely coupled services.  
+
+### **14. What are some common DevOps automation tools?**  
+
+**Answer:**  
+
+- CI/CD: Jenkins, GitHub Actions  
+- Configuration Management: Ansible, Puppet  
+- Infrastructure as Code: Terraform  
+
+### **15. What is Shift-Left Testing?**  
+
+**Answer:** Shift-left testing integrates testing early in the development cycle to detect bugs earlier.  
+
+### **16. What is observability in DevOps?**  
+
+**Answer:** Observability provides insights into system health using logs, metrics, and tracing.  
+
+### **17. What is a rollback strategy?**  
+
+**Answer:** A rollback strategy reverts to a previous stable version if a new deployment fails.  
+
+### **18. What is the role of a DevOps Engineer?**  
+
+**Answer:** A DevOps engineer bridges development and operations, focusing on automation, CI/CD, and cloud management.  
+
+### **19. What are feature flags in DevOps?**  
+
+**Answer:** Feature flags allow toggling features on/off without deploying new code.  
+
+### **20. What is a blue-green deployment?**  
+
+**Answer:** Blue-green deployment maintains two environments, switching traffic between them for zero-downtime updates.  
+
+---
+
+## **Intermediate Level (21-40 Questions)**  
+
+### **21. What is Site Reliability Engineering (SRE)?**  
+
+**Answer:** SRE applies software engineering principles to operations, improving reliability and scalability.  
+
+### **22. How does DevOps help in cloud computing?**  
+
+**Answer:** DevOps automates infrastructure, deployments, and monitoring, making cloud environments scalable and efficient.  
+
+### **23. What is Immutable Infrastructure?**  
+
+**Answer:** Immutable infrastructure replaces servers instead of modifying them, ensuring consistency and reducing drift.  
+
+### **24. How does DevSecOps integrate security into DevOps?**  
+
+**Answer:** DevSecOps embeds security at every stage of the DevOps lifecycle, using automated security scans and compliance checks.  
+
+### **25. What are the benefits of CI/CD pipelines?**  
+
+**Answer:**  
+
+- Faster releases  
+- Automated testing  
+- Reduced manual errors  
+- Enhanced collaboration  
+
+### **26. What is canary deployment?**  
+
+**Answer:** Canary deployment gradually rolls out changes to a small user group before full deployment.  
+
+### **27. What are some common monitoring tools?**  
+
+**Answer:** Prometheus, Grafana, ELK Stack, Datadog, New Relic.  
+
+### **28. What is Configuration Management in DevOps?**  
+
+**Answer:** Configuration management automates infrastructure setup and maintenance. Examples: Ansible, Puppet, Chef.  
+
+### **29. What is GitOps?**  
+
+**Answer:** GitOps manages infrastructure using Git repositories, ensuring version control and automation.  
+
+### **30. How do you handle secrets management in DevOps?**  
+
+**Answer:** Using tools like HashiCorp Vault, AWS Secrets Manager, and Kubernetes Secrets.  
+
+### **31. What is Chaos Engineering?**  
+
+**Answer:** Chaos Engineering tests system resilience by introducing controlled failures.  
+
+### **32. What is a service mesh?**  
+
+**Answer:** A service mesh manages microservices communication using proxies like Istio and Linkerd.  
+
+### **33. What is an API gateway?**  
+
+**Answer:** An API gateway manages API traffic, security, and load balancing.  
+
+### **34. How do you optimize CI/CD pipelines?**  
+
+**Answer:** By parallelizing builds, caching dependencies, and using automated testing.  
+
+### **35. What is hybrid cloud in DevOps?**  
+
+**Answer:** A hybrid cloud combines private and public cloud environments.  
+
+### **36. What is observability vs. monitoring?**  
+
+**Answer:** Monitoring collects data; observability provides deeper insights into system behavior.  
+
+### **37. What are Helm charts?**  
+
+**Answer:** Helm charts package Kubernetes applications for easier deployment.  
+
+### **38. What is A/B testing in DevOps?**  
+
+**Answer:** A/B testing compares different versions of an application to determine the best performance.  
+
+### **39. How do you handle database schema changes in CI/CD?**  
+
+**Answer:** Using tools like Flyway or Liquibase for version-controlled migrations.  
+
+### **40. What is autoscaling in cloud environments?**  
+
+**Answer:** Autoscaling automatically adjusts resource allocation based on demand.  
+
+---
+
+## **Advanced Level (41-60 Questions)**  
+
+### **41. What is the Twelve-Factor App methodology?**  
+
+**Answer:** The Twelve-Factor App is a set of best practices for building modern, scalable cloud applications. The 12 principles focus on aspects like codebase, dependencies, configuration, logging, and disposability.  
+
+### **42. How do you implement zero-trust security in DevOps?**  
+
+**Answer:** Zero-trust security enforces strict identity verification and least-privilege access across the entire system. It includes:  
+
+- Multi-factor authentication (MFA)  
+- Role-Based Access Control (RBAC)  
+- Encryption of data in transit and at rest  
+- Continuous monitoring and logging  
+
+### **43. What are sidecars in Kubernetes?**  
+
+**Answer:** A sidecar is a helper container that runs alongside a main application container within the same pod. Sidecars enhance functionality without modifying the primary application (e.g., logging, monitoring, service mesh).  
+
+### **44. How does Kubernetes handle self-healing?**  
+
+**Answer:** Kubernetes ensures self-healing by:  
+
+- Restarting failed containers  
+- Rescheduling pods on healthy nodes  
+- Automatically scaling replicas  
+- Rolling back deployments if necessary  
+
+### **45. What is progressive delivery?**  
+
+**Answer:** Progressive delivery is an advanced deployment strategy that introduces new changes incrementally to users, using techniques like:  
+
+- **Canary releases** (small group testing)  
+- **Feature flags** (turning features on/off dynamically)  
+- **A/B testing** (comparing multiple versions in production)  
+
+### **46. What is a service mesh, and why is it important?**  
+
+**Answer:** A service mesh (e.g., Istio, Linkerd) is a dedicated infrastructure layer that manages service-to-service communication in microservices architectures. It provides:  
+
+- Traffic control (load balancing, retries)  
+- Security (mutual TLS authentication)  
+- Observability (tracing, metrics, logging)  
+
+### **47. What is GitOps, and how does it improve DevOps workflows?**  
+
+**Answer:** GitOps uses Git repositories as the single source of truth for declarative infrastructure and applications. Benefits include:  
+
+- **Version-controlled deployments**  
+- **Automated reconciliation of state**  
+- **Increased security via RBAC**  
+
+### **48. What is Blue/Green vs. Rolling deployment?**  
+
+**Answer:**  
+
+- **Blue/Green Deployment**: Two identical environments (Blue and Green). Traffic is switched instantly.  
+- **Rolling Deployment**: Gradual update of application instances, minimizing downtime but increasing rollback complexity.  
+
+### **49. How do you handle secrets management in DevOps?**  
+
+**Answer:** Best practices for secrets management include:  
+
+- Using **vault solutions** (e.g., HashiCorp Vault, AWS Secrets Manager)  
+- Avoiding hardcoded secrets in code  
+- Using **environment variables or encrypted configuration files**  
+
+### **50. What is a chaos engineering experiment?**  
+
+**Answer:** Chaos engineering involves intentionally introducing failures to test system resilience. Examples include:  
+
+- **Network disruptions** (latency, packet loss)  
+- **Server crashes** (killing pods or nodes)  
+- **Resource exhaustion** (CPU/memory spikes)  
+
+### **51. How do you implement compliance in DevOps pipelines?**  
+
+**Answer:** Compliance can be enforced using:  
+
+- **Automated security scans** (e.g., SonarQube, Snyk)  
+- **Policy-as-Code** (e.g., Open Policy Agent)  
+- **Audit logging and access controls**  
+
+### **52. What is infrastructure drift, and how do you prevent it?**  
+
+**Answer:** Infrastructure drift occurs when real-world infrastructure deviates from its declared state in code. Prevention methods:  
+
+- **Use Infrastructure as Code (IaC) tools**  
+- **Regularly run drift detection checks**  
+- **Automate infrastructure provisioning**  
+
+### **53. What is a deployment freeze, and when should it be used?**  
+
+**Answer:** A deployment freeze is a temporary halt on new releases, typically during critical business periods (e.g., holiday sales, tax season).  
+
+### **54. How do you ensure high availability in a DevOps environment?**  
+
+**Answer:** High availability can be ensured through:  
+
+- **Multi-region deployments**  
+- **Load balancing & auto-scaling**  
+- **Database replication & failover mechanisms**  
+
+### **55. What is a multi-cloud strategy?**  
+
+**Answer:** A multi-cloud strategy uses multiple cloud providers (e.g., AWS, Azure, GCP) to:  
+
+- Reduce vendor lock-in  
+- Improve redundancy and fault tolerance  
+- Optimize costs  
+
+### **56. How does FinOps fit into DevOps?**  
+
+**Answer:** FinOps (Financial Operations) helps manage cloud spending efficiently. Practices include:  
+
+- **Cost monitoring tools** (AWS Cost Explorer, Azure Cost Management)  
+- **Auto-scaling and right-sizing resources**  
+- **Tagging and budgeting policies**  
+
+### **57. What are the challenges of DevOps adoption in large enterprises?**  
+
+**Answer:**  
+
+- **Legacy system integration**  
+- **Security and compliance concerns**  
+- **Cultural resistance to automation**  
+- **Skill gaps within teams**  
+
+### **58. What is a Kubernetes operator?**  
+
+**Answer:** A Kubernetes Operator automates complex application lifecycle management tasks by extending Kubernetes capabilities using custom controllers.  
+
+### **59. What are observability pillars in DevOps?**  
+
+**Answer:** The three pillars of observability are:  
+
+- **Logs** (text-based records of system events)  
+- **Metrics** (numerical measurements like CPU usage)  
+- **Tracing** (tracking requests across distributed systems)  
+
+### **60. What are the best practices for incident response in DevOps?**  
+
+**Answer:**  
+
+- **Automated alerts and monitoring** (PagerDuty, Prometheus)  
+- **Runbooks and playbooks for issue resolution**  
+- **Post-mortems for continuous learning**