To begin with, this bachelor thesis explains features of non-relational (NoSQL) databases, in this case that is the MongoDB database, as well as primary differences between non-relational and relational databases. Primary data operations in MongoDB database are presented with accompanying examples for specific operations. The next chapter lists necessary technologies for creating a simple web application. The Node.js platform in which the server side is implemented is described more closely, as well as the Express.js framework, JavaScript (a simple programming language that enables communication between the client and the server program) and the usage of MongoDB database in Node.js environment with simple corresponding examples. Furthermore, the next chapter is focused on the purpose of React.js library with its features on the client side, as well as the creation of React application. The theoretical part is followed by the practical part of this bachelor thesis which shows the development of a simple application that allows non-relational database manipulation. The snapshots of the programming code and the user interface allow easier understanding of the use of technologies and app development. At the very end, the summary rounded off the topic of the bachelor thesis – reason behind the usefulness of non-relational databases and the way of using them in web application development.