Composer is an application-level package manager for the PHP programming language that provides a standard format for managing dependencies of PHP software and required libraries. It manages them on a per-project basis, installing them in a directory (e.g. vendor) inside your project.
Unlike compiled languages, in PHP if you make a mistake, the program will crash when the line of code with the mistake is executed. When testing a PHP application, whether manually or automatically, developers spend a lot of their time discovering mistakes that wouldn’t even compile in other languages, leaving less time for testing actual business logic.
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.
Rsync is a very flexible network-enabled syncing tool. Due to its ubiquity and its popularity as a tool for system scripts, it's included on most Linux distributions by default. It efficiently copies and sync files to or from a remote system. It’s faster than scp because rsync uses a remote-update protocol which allows transferring just the differences between two sets of files. The first time, it copies the whole content of a file or a directory from source to destination but from next time, it copies only the changed blocks and bytes to the destination.