software engineering Software engineering is a branch of both computer science and engineering focused on designing, developing, testing, and maintaining Application software, software applications. It involves applying engineering design process, engineering principl ...

, a monolithic application is a single unified

software application Application software is any computer program that is intended for end-user use not computer operator, operating, system administration, administering or computer programming, programming the computer. An application (app, application program, sof ...

that is self-contained and independent from other applications, but typically lacks flexibility. There are advantages and disadvantages of building applications in a

monolith A monolith is a geological feature consisting of a single massive stone or rock, such as some mountains. Erosion usually exposes the geological formations, which are often made of very hard and solid igneous or metamorphic rock. Some monolit ...

ic style of

software architecture Software architecture is the set of structures needed to reason about a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements a ...

, depending on requirements. Monolith applications are relatively simple and have a low cost but their shortcomings are lack of elasticity,

fault tolerance Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems. Fault t ...

and

scalability Scalability is the property of a system to handle a growing amount of work. One definition for software systems specifies that this may be done by adding resources to the system. In an economic context, a scalable business model implies that ...

. Alternative styles to monolithic applications include

multitier architecture In software engineering, multitier architecture (often referred to as ''n''-tier architecture) is a client–server architecture in which presentation, application processing and data management functions are physically separated. The most wide ...

distributed computing Distributed computing is a field of computer science that studies distributed systems, defined as computer systems whose inter-communicating components are located on different networked computers. The components of a distributed system commu ...

and

microservices In software engineering, a microservice architecture is an architectural pattern that organizes an application into a collection of loosely coupled, fine-grained services that communicate through lightweight protocols. This pattern is characterize ...

. Despite their popularity in recent years, monolithic applications are still a good choice for applications with small team and little complexity. However, once it becomes too complex, you can consider refactoring it into microservices or a distributed application. Note that a monolithic application deployed on a single machine, may be performant enough for your current workload but it's less available, less durable, less changeable, less fine-tuned and less scalable than a well designed

distributed system Distributed computing is a field of computer science that studies distributed systems, defined as computer systems whose inter-communicating components are located on different networked computers. The components of a distributed system commun ...

. The design philosophy is that the application is responsible not just for a particular task, but can perform every step needed to complete a particular function. Some personal finance applications are monolithic in the sense that they help the user carry out a complete task, end to end, and are private data silos rather than parts of a larger system of applications that work together. Some

word processor A word processor (WP) is a device or computer program that provides for input, editing, formatting, and output of text, often with some additional features. Early word processors were stand-alone devices dedicated to the function, but current word ...

s are monolithic applications. These applications are sometimes associated with

mainframe computers A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterpris ...

. In software engineering, a monolithic application describes a software application that is designed as a single service. Multiple services can be desirable in certain scenarios as it can facilitate maintenance by allowing repair or replacement of parts of the application without requiring wholesale replacement. Modularity is achieved to various extents by different

modular programming Modular programming is a software design technique that emphasizes separating the functionality of a program into independent, interchangeable modules, such that each contains everything necessary to execute only one aspect or "concern" of the d ...

approaches. Code-based modularity allows developers to reuse and repair parts of the application, but development tools are required to perform these maintenance functions (e.g. the application may need to be recompiled). Object-based modularity provides the application as a collection of separate executable files that may be independently maintained and replaced without redeploying the entire application (e.g. Microsoft's

Dynamic-link library A dynamic-link library (DLL) is a shared library in the Microsoft Windows or OS/2 operating system. A DLL can contain executable code (functions), data, and resources. A DLL file often has file extension .dll even though this is not required ...

(DLL); Sun/UNIX shared object files). Some object messaging capabilities allow object-based applications to be distributed across multiple computers (e.g. Microsoft's

Component Object Model Component Object Model (COM) is a binary-interface technology for software components from Microsoft that enables using objects in a language-neutral way between different programming languages, programming contexts, processes and machines ...

(COM)).

Service-oriented architecture In software engineering, service-oriented architecture (SOA) is an architectural style that focuses on discrete services instead of a monolithic design. SOA is a good choice for system integration. By consequence, it is also applied in the field ...

s use specific communication standards/protocols to communicate between modules. In its original use, the term "monolithic" described enormous mainframe applications with no usable modularity. This, in combination with the rapid increase in computational power and therefore rapid increase in the complexity of the problems which could be tackled by software, resulted in unmaintainable systems and the "

software crisis Software crisis is a term used in the early days of computing science for the difficulty of writing useful and efficient computer programs in the required time. The software crisis was due to the rapid increases in computer power and the complex ...

Patterns

Here are common

architectural pattern Software architecture pattern is a reusable, proven solution to a specific, recurring problem focused on architectural design challenges, which can be applied within various architectural styles. Examples Some examples of architectural patte ...

s used for monolithic applications, each has its own trade-offs: * Layered architecture * Modular monolith * Microkernel architecture

References

Software architecture History of software {{soft-eng-stub