A Clustered Index is a database indexing technique that helps in optimizing query performance by storing data in a sorted order based on the indexed columns. This physical ordering of data on the disk allows for faster retrieval of rows, especially when queries involve range-based searches or sorting. However, it's important to note that a table can have only one clustered index.

The "git branch" command, when used without any additional arguments, lists all existing branches in the Git repository. It's a handy command to see the available branches and the currently active branch.

PHP is a server-side scripting language commonly used for web development. It allows developers to create dynamic web pages and interact with databases on the server side.

Composition and inheritance are both mechanisms for reusing code in OOP, but they differ in their approach. Composition involves creating complex objects by combining simpler ones, whereas inheritance involves creating a new class based on an existing class, inheriting its properties and behavior.

The command used to stage files for committing in Git is git add. This command adds changes to the staging area, preparing them for the next commit. It allows for selective committing of changes.

SDLC stands for Software Development Life Cycle. It is a systematic process for planning, creating, testing, deploying, and maintaining information systems.

AWS Lambda is the AWS service used for serverless computing. It allows developers to run code without provisioning or managing servers. It's a cost-effective way to build applications that respond to events and scale automatically.

In GitHub Flow, a pull request is typically merged into the main branch after it has undergone code review, received approvals, and any required tests have passed. This ensures the quality and integrity of the main branch.

In response to a critical production issue, the key step is to conduct a root cause analysis. This involves identifying the underlying cause of the problem to implement a targeted solution. Rolling back may be necessary, but preventing future incidents requires understanding and addressing the root cause.

To troubleshoot rendering issues in different browsers, the Elements panel helps inspect and modify HTML and CSS. It allows real-time adjustments to ensure the page renders correctly.