CDNs cache content on multiple servers globally, reducing latency by serving content from the nearest server to the user. This optimizes performance by minimizing the distance data travels.

A graph database is best suited for hierarchical data storage. It represents data in the form of nodes and edges, making it efficient for storing and querying hierarchical relationships.

For a microservices-based web application, Java with Spring Boot is a robust choice. Spring Boot provides a well-structured and modular framework for building microservices, ensuring scalability and maintainability.

When facing a sudden spike in error rates, analyze error patterns, identify recent changes in the codebase or configuration, and check dependencies for issues. This proactive approach helps pinpoint the cause and take appropriate action. Ignoring the spike or increasing server capacity without investigating the root cause is a reactive strategy that may not address the underlying issue. Disabling error logging temporarily hinders troubleshooting efforts.

Gitflow and GitHub Flow differ in their branching models. Gitflow tends to be more complex, with designated branches for features, releases, and hotfixes. GitHub Flow, on the other hand, is simpler, focusing on branches for features and releases in a more continuous delivery style.

One way to reduce the frequency of merge conflicts in Git is by regularly rebasing branches with the main development branch. Rebasing incorporates the changes from one branch into another, maintaining a cleaner and linear project history.

Multi-Version Concurrency Control (MVCC) works by creating a new version of a modified data item for each transaction. This allows multiple transactions to access different versions of the same data concurrently, promoting better concurrency and reducing contention for resources.

The Observer pattern is appropriate for scenarios where multiple modules need to be notified of changes in another object. It establishes a one-to-many dependency between objects, ensuring that when one object changes state, all its dependents are notified and updated automatically.

The Iterator design pattern is used to provide a way to access elements of an aggregate object sequentially without exposing its underlying representation. It abstracts the traversal mechanism and allows the client to access elements without knowing the internal structure.

IaC stands for Infrastructure as Code. It is a key DevOps practice that involves managing and provisioning computing infrastructure through machine-readable script files, rather than through physical hardware configuration or interactive configuration tools.