A callback is a piece of code (i.e. the address or reference of a function or method or a lambda expression) that is passed as an argument to other code, which is expected to call back (execute) the argument at some convenient time. This tag should be used with questions about an API that uses call backs to notify the caller when an action is complete. Use the event-handling tag for questions involving subscribing to events such as in a GUI framework.

GNU Emacs is an extensible, customizable, self-documenting text editor, which can be extended with Lisp code. Although Emacs is a general-purpose editor, questions may be on-topic here if they are about extending Emacs itself (usually by writing Emacs Lisp functions) or about specific programming modes. Otherwise (and perhaps also in those cases), consider asking your question on Emacs Stack Exchange.

Apache JMeter is an open source Java application, designed to load-test functional behavior and measure performance. Originally designed for testing Web Applications, it has since expanded to other test functions as well.

Configuration is the process of specifying the settings used for a system or application

Clojure is a modern Lisp dialect for the Java Virtual Machine (with versions for the CLR and JavaScript). More than merely an implementation of Lisp in Java, Clojure provides access to Java's classes and ecosystem.

Cron is a time-based job scheduler running as a daemon process in Unix-like computer operating systems.

Play Framework is a modern open-source web framework for Java and Scala.

Safari is Apple's web browser, the default browser on macOS and iOS.

In computing, input/output, or I/O, refers to the communication between an information processing system (such as a computer), and the outside world, possibly a human, or another information processing system.

This tag is non-specific. Use a specific script tag instead. The following tags are much more specific: [awk] [bash] [bat] [google-apps-script] [javascript] [perl] [php] [python] [ruby] [sh] [powershell]

Doctrine ORM is a PHP ORM. While Doctrine 1.2 uses the Active Record pattern, Doctrine ORM 2 and up uses the Data Mapper pattern. The Doctrine project is a collection of open source libraries and tools for dealing with database abstraction and Object-Relational Mapping written in PHP.