Continuous integration (CI) and continuous delivery (CD) are essential for modern software teams, as there is now a need for fast feature delivery and high-velocity improvements. However, achieving high speed may be difficult without compromising reliability, as the process involves coordinating among development teams working on different features of the same application simultaneously, product complexity and possible bottlenecks. Nevertheless, even in this challenging case, proper practices and tools can help these teams succeed.  

Definition and Purpose of CI/CD 

Elaborating on the terms, CI refers to merging code changes into a shared repository where automated builds and tests validate each update. On the other hand, CD, besides these operations, also automates the releases of validated code to production or staging. CI/CD’s goal is to detect code-related issues, reduce manual efforts and deliver new features as quickly as possible.  

Why Velocity Matters 

Velocity, which measures how fast teams deliver working software, indicates their productivity. For example, high velocity rates show that teams deliver features and respond to customer needs fast. In contrast, low velocity highlights that a team needs to improve the pace of releases, bug fixes, or other items. Although velocity mainly concerns speed, it also demonstrates whether the tooling, processes and team collaboration are suitable and whether developers can work efficiently.  

CI/CD-Related Challenges in Large Teams  

As the teams expand, the complexity of CI/CD also increases. Thus, the most common issues are:  

1. Merge/integration conflicts occur more frequently because more developers make more code commits. 
2. Shared codebases can cause failures that will affect multiple teams.  
3. Building and testing pipelines are critical for developers. If they are too slow, it reduces velocity.  
4. As the requirements for speed are high, this may lead teams to cut corners to achieve them, which is risky in terms of production outcomes.  

Building a Resilient CI/CD Infrastructure  

Large teams need various approaches to pipelines and infrastructure to overcome the issues mentioned before. The following are examples of possible approaches.  

1. Modular: it allows you to separate errors and facilitate troubleshooting. For example, to build, then lint, unit test, integration test and finally deploy. 
2. Parallelisation: running tests and builds simultaneously to reduce overall pipeline time.  
3. Scalability: using containers (for example, Docker) and cloud infrastructure (GitLab CI, CircleCI) to scale pipelines’ storage capacity on demand.  
4. Pipeline as a code: storing pipeline configurations in version control (YAML, Jenkins) to improve transparency.  
5. Environment management: using temporary environments for feature testing. This approach will help reduce conflicts and failures when building in real-life conditions.  

Tips for Collaboration and Code Quality  

There are tips for improving collaboration and code quality. For example, besides isolating changes, encourage peer review among developers and invest in testing in every stage (unit, integration, end-to-end). Moreover, require all pull requests to pass automated checks before merging and prevent unreviewed code from being released. If failures happen, analyse them without prejudice and learn from them. 

Team communication also matters in large teams. For instance, developers should define what “done” means and ensure everyone knows how to escalate issues. For tracking pipeline health, use specialised dashboards (Datadog, Buildkite). Use email to receive notifications when builds fail. Lastly, continuously review and remove bottlenecks.  

Toolkit  

1. CI/CD platforms: Jenkins, GitHub Actions, GitLab CI, CircleCI, Azure DevOps 
2. Infrastructure as code: Terraform, Ansible  
3. Test orchestration: Cypress, Selenium Grid, Playwright  
4. Monitoring/alerting: Prometheus, Sentry, PagerDuty  

Conclusion 

In conclusion, maintaining velocity and reliability is possible by investing in a scalable architecture, pipeline health, segmentation, testing and automation. Clear and compelling team communication, as well as reviewing bottlenecks, are necessary to build CI/CD pipelines as living systems.