Scenario and Challenges
Sure, here's a mock interview-style Q&A where you're explaining a real-time scenario of migrating from Jenkins to GitHub Actions, including challenges faced and how you solved them, in a clear and confident way:
👤 Interviewer: You mentioned that you migrated from Jenkins to GitHub Actions. Can you walk me through a real scenario during that migration—what challenges did you face and how did you handle them?
👨💻 Pavan (You): Sure. One of the major projects I worked on involved migrating over 20+ Jenkins pipelines—both freestyle and scripted—to GitHub Actions for microservices hosted on Kubernetes.
One specific challenge we faced was replicating Jenkins Shared Libraries functionality in GitHub Actions. In Jenkins, we had a centralized repo for reusable Groovy scripts that managed build steps like Docker image creation, vulnerability scanning, and Helm chart deployments. GitHub Actions doesn’t have an exact equivalent, so we had to modularize the logic using composite actions and reusable workflows.
To solve this, I created a set of composite actions stored in a .github/actions directory within each repo or centralized them in a separate repo and referenced them using uses: in workflows. This helped maintain DRY principles and allowed the team to update logic across workflows easily.
👤 Interviewer: Interesting. What about secret management? Did you face any issues?
👨💻 Pavan: Yes, secret management was another key area. In Jenkins, we used plugins like HashiCorp Vault or stored secrets in the Jenkins credential store. In GitHub Actions, we moved to GitHub Secrets and Environment Secrets, but we had to implement tighter permission controls.
One mistake we initially made was storing sensitive credentials at the repo level for all environments. We later moved to Environment-scoped secrets, which allowed us to set approval workflows for production deployments. This gave better separation between staging and production environments.
👤 Interviewer: Did you encounter any issues related to pipeline performance or self-hosted runners?
👨💻 Pavan: Yes, pipeline execution time was a concern. Our Jenkins setup had powerful self-hosted agents that were optimized for parallel builds. Initially, GitHub-hosted runners were slower and limited concurrency became a bottleneck.
To solve this, we deployed self-hosted GitHub runners using autoscaling groups on AWS EC2. We used a GitHub Actions Runner Controller (GARC) in Kubernetes for dynamic scaling based on job demand, which brought performance close to what we had on Jenkins.
👤 Interviewer: What would you say was the biggest lesson or takeaway from this migration?
👨💻 Pavan: The biggest takeaway was the importance of standardization and modular design. GitHub Actions is extremely powerful but only if workflows are built in a reusable and maintainable way. Also, involving the team early, creating clear documentation, and running shadow pipelines alongside Jenkins before cutover helped build confidence and reduce risk.
Absolutely! Here’s a continuation of the mock interview with different real-time challenges you might’ve faced while migrating from Jenkins to GitHub Actions, along with practical solutions, presented in an interview-style format:
👤 Interviewer: That’s great insight. Any other technical challenges you encountered during the migration?
👨💻 Pavan:
Yes, another challenge was handling multi-branch pipeline strategies. In Jenkins, we used the Multibranch Pipeline feature to dynamically trigger jobs for every branch or PR. Replicating that in GitHub Actions required us to restructure our workflows using on: push, on: pull_request, and filters like branches and paths.
But GitHub Actions lacks first-class UI-based visibility for branches like Jenkins does. To overcome this, we standardized workflow templates and added detailed status checks and badges in PRs using the actions/github-script and checks APIs to provide real-time pipeline insights in GitHub UI itself.
👤 Interviewer: How did you manage build artifact storage and retention, especially coming from Jenkins where you have custom retention policies?
👨💻 Pavan:
Exactly, in Jenkins we had artifact archiving plugins and customized retention scripts. In GitHub Actions, artifacts are stored using the actions/upload-artifact and download-artifact actions, but their retention defaults were lower.
So, we had to explicitly set retention-days in our workflows. For long-term storage like logs or release packages, we integrated Amazon S3 as a secondary storage using a custom action to sync critical artifacts post-build. This ensured we didn’t rely only on GitHub’s limits.
👤 Interviewer: How did you ensure production deployment safety during this switch?
👨💻 Pavan:
We couldn’t afford downtime, so we used a blue-green strategy for pipeline migration. We kept Jenkins pipelines intact and ran GitHub workflows in dry-run mode in parallel, validating every stage like image builds, scanning, and Helm deployment using --dry-run.
Once validated, we switched GitHub Actions to live mode but gated production deployments using manual approvals via Environments. This allowed rollback to Jenkins instantly in case of failure without impacting production.
👤 Interviewer: Did you face any team adoption or usability issues?
👨💻 Pavan: Yes, that was a soft but real challenge. Some developers were deeply familiar with Jenkins and hesitant to adopt GitHub Actions YAML syntax and its debugging.
To resolve this, I created internal documentation with visual diagrams, added inline comments in workflows, and hosted a knowledge-sharing session to walk through common patterns. We also created workflow templates using workflow_call so that developers didn’t need to write from scratch.
This helped adoption and ensured pipelines remained consistent across all microservices.
👤 Interviewer: Last one — what about plugin dependencies? Jenkins has a huge plugin ecosystem.
👨💻 Pavan: Absolutely. Some Jenkins jobs depended on plugins like Slack Notifier, SonarQube Scanner, and Build Timestamp. These weren’t directly available in GitHub Actions.
So we replaced them with corresponding open-source actions from the GitHub Marketplace, or we wrote custom shell-based steps where needed. For Slack notifications, we used 8398a7/action-slack with incoming webhooks. For SonarQube, we used their official CLI wrapped in a Docker container.
We ensured we tested each plugin-equivalent thoroughly before fully retiring Jenkins.
Would you like me to compile all of this into a crisp one-pager you can use as interview prep notes?
Last updated