What is the software development life cycle (SDLC)?

The SDLC breaks down software development into distinct, repeatable stages and provides a roadmap that helps organizations create software that meets stakeholder needs and customer expectations throughout the software’s lifecycle. Each phase of the SDLC has its own objectives and specific deliverables that help guide the next phase of software development.

Different SDLC models approach these phases in different ways. In some models, such as the waterfall model, the stages are completed sequentially. In others, such as iterative processes like agile, stages can be worked on in parallel. The chosen development model usually depends on organizational needs and priorities and project requirements.

Software development involves the balancing of many factors that present challenges to development teams. Teams must consider and incorporate the needs of various stakeholders, changing requirements and resource availability, how a product fits into the greater IT environment, how any updates might impact its integration and much more. The SDLC provides a framework that development teams use to work through these factors and create successful software.

Among other benefits, the SDLC helps stakeholders estimate project costs and time frames and identify and minimize risks by addressing risk factors early on in development. It also helps measure development progress, enhance documentation and transparency and better align software projects with organizational goals.

While the specific details of the SDLC methodology will vary from team to team, the software development life cycle is often described in six stages. Some models make planning and analysis discrete stages, for a development life cycle with seven stages.

The stages of the SDLC include:

• Planning and analysis
• Design
• Development
• Testing
• Deployment
• Maintenance

Each phase of the SDLC has distinct tasks and objectives and—as a whole—is intended to provide a standardized roadmap that covers all aspects of software development.

The planning phase establishes the goals and scope of a software development project. During the project planning stage, the software development team brainstorms basic, high-level ideas about the project. These ideas include the problem or use case it will solve, who will use it and how the software might interact with other applications and systems.

The development team conducts market research and feasibility testing, evaluates prototypes, allocates resources and completes requirements gathering. The software development team solicits input from stakeholders including business analysts, line-of-business managers, internal and external customers and other developers to pinpoint the project’s goals. Importantly, teams also establish what is not needed to prevent the project from becoming too bloated. Sometimes, requirements analysis is split into its own phase.

The development team also drafts a software requirement specification (SRS) document that helps the team stay on task throughout the project. The SRS includes the software’s functions, necessary resources, possible risks and a project timeline. By the end of the planning stage, the software development team understands the project’s business goals and the risks involved.

Before the developers can write code, they must first design the project’s architecture. The design phase involves outlining the software’s navigation, user interfaces, database design and more. Many modern organizations use a microservices architecture when building new software applications. Microservice is a cloud-native architectural approach in which a single application is composed of many loosely coupled and independently deployable smaller components or services.

In this stage, developers also assess how the software fits into an organization’s existing landscape of apps and services, both upstream and downstream and any other dependencies it will have. Development teams work together to create a prototype that is both easy to operate for end users and easy to integrate into an organization’s current systems.

Sometimes designers create a prototype, or multiple prototypes, of the software to show stakeholders what the product might look like and to solicit feedback. All this work is collected in a software design document (SDD), which is passed on to developers as a roadmap to use while coding.

The development phase is when the team starts to write the code and build the software, using documents including the SDD and SRS as guidelines. These documents help guide software developers and engineers in choosing the correct programming language, such as Java or C++ and help project managers divide the project into smaller, discrete coding tasks.

Programmers and developers also build any additional systems or interfaces necessary for the software to function properly, such as web pages or application programming interfaces (APIs). Throughout the development stage, it’s important that teams perform regular code tests and reviews to identify bugs and other vulnerabilities.

After the development team has created a functional piece of software, it’s now time to refine it to eliminate bugs and look for opportunities to enhance the final product.

A quality assurance team might perform unit testing, integration testing, system testing, acceptance testing and other types of testing to make sure that all parts of the software work as intended. They make sure that it meets user and business requirements and works within the organization’s broader IT environment.

Testers will also scrutinize the software for security vulnerabilities at this stage, identify when and how they occur and document the findings. Developers then address the bugs, implement fixes and send the software back to be tested again.

Both manual and automated testing is used in this process. AI tools are often used during software testing—for instance, to generate test cases and analyze patterns in test failures. In many instances, such as in agile, V-shaped and spiral models, continuous testing (CT) is employed as part of the model and code is tested throughout the development process (not just at the end).

When a software product is finely tuned and all known bugs have been fixed, then it can be deployed to the production environment where users can access it. The goal of this stage isn’t just to get the software in the hands of users. The goal is also to make sure that they understand how to use it and that it can be deployed with minimal disruption to the user experience or workflow.

This might involve deploying software in stages—such as a beta release, where a limited group of users tests an early version of the software—before releasing it to the public. It might also be necessary to create manuals, conduct training sessions, or offer onsite support for users.

The SDLC doesn’t end when the software is deployed. Despite thorough testing, there are always unanticipated fixes, new use cases and software optimizations that must be addressed postdeployment. Ongoing maintenance and support are necessary to safeguard the longevity of any given piece of software. Think of it like remodeling a house—over time, small pieces will be misused or break down and will have to be replaced and hopefully, improved.

During this phase of the SDLC, software engineers continue to push software updates, test fix patches and squash any new bugs that users find. In some development models, such as DevOps models, teams use continuous integration and continuous deployment (CI/CD). This is an approach where code is continuously added to the code base as it is written, continuously tested and automatically deployed to the production environment.

There are many different software development models. Some of the most popular SDLC models are:

• Waterfall
• V-shaped
• Agile
• Lean
• Iterative
• Spiral
• Big bang

Choosing the right SDLC model depends on various factors. Are the project requirements clearly defined, or likely to change during the development process? How complex is the project? How experienced is the development team? Answering these questions can help stakeholders choose the most appropriate model for a project.

While the waterfall model is less common today than it was in the past, it’s the basis for many subsequent SDLC models. It is a linear, sequential model in which one stage is finished before the next is started. It provides a structured, predictable process that works for well-defined, stable projects.

This model is very inflexible in that it is difficult and time-consuming to return and correct previous stages once completed.

This model is a variation on the waterfall model and is sometimes called the “verification and validation” model. In the V model, each phase of the SDLC has its own accompanying testing phase. This frequent testing helps eliminate bugs early on, but the linear structure makes the V (like the waterfall model) less flexible than other methodologies.

The agile model is designed to be responsive to changing requests or requirements and to help accelerate production. This is done through continuous development cycles, with small, incremental changes from previous releases.

The idea behind this approach is that by identifying small problems during the development process, the problems can be dealt with before they snowball into bigger problems. Variations on the agile methodology—sometimes known as “frameworks”—define roles in the development team to make this process even faster. Two of the most common agile frameworks are “scrum” and “kanban.”

The goal of a lean model is to continuously improve business processes during development. This model is all about efficiency and hitting important short-term goals, iterating on the process after each step to cut out bloat.

This model focuses on starting with a small goal and then building outward from there. In the iterative model, an initial version of the software is created quickly and then improved rapidly with successive versions.

The spiral model has a specific focus on the risk patterns of a project. In this model, development repeats in a spiral over time. Planning, resource and risk analysis, development and testing occur repeatedly during development to try to cover every possible scenario before deployment. This model is ideal for complex projects with frequent changes.

This is an informal and unstructured form of software development that lacks the rigorous definition of each stage normally associated with the SDLC. Like the theory of the big bang, this is a model that starts from nothing—no planning or requirement analysis—and is considered high risk. The big bang model can work well for small projects where the parameters of the project are self-explanatory.

DevOps is a software development methodology that accelerates the delivery of high-quality applications and services by combining and automating the work of software development and IT operations teams. The core principles of a DevOps approach are collaboration, automation and continuous integration and continuous delivery (CI/CD).

The definition of SDLC has broadened from one specific method for software development to any lifecycle used for end-to-end software development. Because DevOps addresses the full software development process, it can be considered a software development lifecycle itself. But DevOps is also larger than that, encompassing a cultural and organizational shift toward shared responsibility and collaboration. Crucially, DevOps is not a model, but a combination of practices, tools and cultural philosophies.

The DevOps lifecycle has its own steps, steps that are similar to those of the SDLC. A simplified way to put it is that DevOps takes the steps of the SDLC and reconfigures them to create a continuous cycle for software development and improvement.

DevOps addresses the rigidity of the SDLC by making each stage of the software development process continuous throughout the project. The planning, coding, building, testing, deploying, releasing, operating and monitoring continues throughout a product’s lifecycle, creating a continuous delivery pipeline that improves software through frequent updates.

DevSecOps is DevOps that automates the integration of security and security practices at every phase of the software development life cycle. Traditional software development adds security testing as its own, discrete stage of development. Using the principles of DevOps, which is built around the continuous delivery of updates, each step of the SDLC incorporates security considerations.

By making security an aspect of each phase of development, teams can avoid delays due to security issues, create more secure programs, accelerate vulnerability patching and deliver more cost-effective software.

The agile model is one of the most popular SDLC models because it emphasizes collaboration, continuous delivery and customer feedback. This iterative methodology breaks large projects down into fast-paced “sprints”—smaller tasks with discrete goals meant to be completed in short time frames. The idea is to keep the team feature-driven during the development process and enable teams to quickly identify problems and respond to changing requirements and user needs.

Scrum is an agile project management framework that some development teams apply to their software development process. Its name comes from the sport of rugby. In rugby, a scrummage is a way to restart play after possession of the ball has been lost that relies on clear communication between players working in unison. In the agile framework, scrum also asks team members to act as cohesive units that necessitate teamwork and open collaboration.

In the scrum framework, development teams are broken down into smaller units, led by a “scrum master.” The scrum master answers to the product owner, who also acts as the point of contact between each scrum team. These small teams are encouraged to take ownership over the task assigned to them during each sprint, allowing for adaptability and creative solutions without needing to stop and wait for feedback from other stakeholders.

For scrum to work as intended, these teams must be open with each other and in constant communication, just like a sports team when the pressure is on.

Overall, the SDLC helps organizations create high-quality software. It delivers many specific benefits, including:

• Deliver higher-quality software
• Increase productivity
• Minimize risk
• Improve project transparency and visibility
• Promote collaboration
• Efficiently manage costs and resources
• Improve customer satisfaction

The SDLC provides a map that helps teams complete any software development project, no matter how complex, within scheduled time frames and cost estimates. In addition, it emphasizes testing and quality assurance as part of the process, increasing overall product and code quality.

The structure of the SDLC helps streamline projects and eliminate guesswork. With clear documentation to guide progress between stages, the SDLC can reduce software production time and boost development productivity.

The SDLC helps organizations account for project risk. In some SDLC models, risk assessment is performed continuously throughout the development process. These models are designed to identify risks in the beginning of the project so that small problems don’t grow into big ones as the project progresses.

The SDLC promotes transparency with processes that inform stakeholders of what’s already been accomplished, what needs to be accomplished and what their own personal responsibilities are. By creating documentation of the process during development, all stakeholders understand the work that’s come before them and can use that knowledge in completing their own tasks.

By providing a visible, documented plan, SDLC models promote open communication between stakeholders regarding software goals, pain points and more. In some models and methodologies, team members are encouraged to form small, highly collaborative groups to find creative solutions to development problems.

Estimating the overall costs of development is an important part of the SDLC process. Before development begins, all stakeholders should understand the resources required to complete the project. Documentation created throughout each stage of the SDLC can be used to decrease bloat and keep projects on task and on budget.

The SDLC helps create software that doesn’t suffer from feature bloat, is easy for users to understand and use and fits into an organization’s existing IT landscape. Software that has been rigorously planned, executed and tested by following an SDLC framework should also have fewer bugs when deployed.