Object-oriented programming (OOP) is based on the concept of 'objects', which can contain data and code to manipulate that data. Functional programming focuses on writing functions that take inputs and produce outputs without modifying state or data. OOP emphasizes encapsulation, inheritance, and polymorphism, while functional programming emphasizes immutability and first-class functions.

I primarily use Git for version control. I create branches for new features or bug fixes, commit changes with clear messages, and create pull requests for code reviews. I also use tags for marking releases and I am familiar with rebasing and merging to keep the project history clean.

RESTful API design principles include statelessness, where each request from the client to the server must contain all the information needed to understand and process the request; resource-based URLs, which use nouns rather than verbs for endpoints; and using standard HTTP methods like GET, POST, PUT, DELETE. Responses should be in a format that API consumers can consistently parse, such as JSON, and proper status codes should be returned to indicate the result of the operation.

SQL databases are relational, meaning they store data in tables and use structured query language for defining and manipulating that data. They are best suited for complex queries and transactions. NoSQL databases are non-relational and can store data in formats like key-value pairs, documents, wide-columns, or graphs, making them more flexible for unstructured data and horizontal scaling. NoSQL databases are often preferred for large-scale, distributed data storage needs.

To optimize the performance of a web application, I focus on efficient algorithms and data structures, reducing server response times by optimizing database queries, using caching mechanisms, minimizing the loading of resources through lazy loading and code splitting, implementing compression techniques, and ensuring good client-side performance by optimizing frontend code, images, and other assets.

Continuous integration (CI) is a development practice where developers frequently integrate their code into a shared repository, typically several times a day. Each integration is verified by an automated build and automated tests, which helps detect errors quickly. To implement CI, I use tools like Jenkins, Travis CI, or GitHub Actions to set up the automated build process. The CI pipeline includes steps such as code checkout, build, unit tests, integration tests, and deployment.