server

MongoDB is a popular open source and document oriented database system. It belongs to a family of databases called NoSQL, which is different from the traditional table based SQL databases. It makes use of collections, each having multiple documents, and allows the user to store data in a non relational format. Data is stored in flexible, JSON-like documents where fields can vary from document to document. That's the reason for calling it schemaless database.

Redis is an open-source in-memory key-value data store. It can be used as a database, cache, message broker and supports various data structures such as Strings, Hashes, Lists, Sets, etc... Apart from its performance and flexibility, Redis stands out with its wide language support, high availability, and automatic partitioning.

MySQL is an open-source relational database management system (RDBMS). Its name is a combination of My and SQL the abbreviation for Structured Query Language. A relational database organizes data into one or more data tables in which data types may be related to each other; these relations help structure the data. SQL is a language programmers use to create, modify and extract data from the relational database, as well as control user access to the database.

Symfony is a PHP web application framework and a set of reusable PHP components/libraries. Symfony aims to speed up the creation and maintenance of web applications and to replace repetitive coding tasks. It's also aimed at building robust applications in an enterprise context, and aims to give developers full control over the configuration: from the directory structure to the foreign libraries, almost everything can be customized.

Many applications start their web server and database hosted on the same machine. It's simpler, cheaper and easier to manage. However, as our application grows , a setup like this can bring security issues and scalability problems. A common solution is to separate our database from the application: creating a dedicated database server and allowing applications to connect remotely. This setup is more secure, it can provide you a better analysis of the bottlenecks and definitely makes the scalability easier.

An Apache web server can host multiple websites on the SAME server. You do not need separate server machine and Apache for each website. This can be achieved using the concept of Virtual Host or VHost.
Any domain that you want to host on your web server will have a separate entry in Apache configuration file.

Apache or Apache HTTP server is a free and open source web server, developed and maintained by the Apache Software Foundation. It is one of the most popular web servers in the world. Apache allows website developers to serve their content over the web and provides many powerful features that can be extended through additional modules.