Understanding the SDLC: Software Development Lifecycle Explained

Building great software is a big challenge, and development teams rely on the software development lifecycle (SDLC) to help them succeed. By providing a structured approach to software development, an effective SDLC helps teams:

• Clarify and understand stakeholder requirements.

• Estimate project costs and timeframes.

• Identify and minimize risks early in the process.

• Measure progress and keep projects on track.

• Enhance transparency and improve client relations.

• Control costs and accelerate time to market.

What is SDLC?

The software development lifecycle (SDLC) is a step-by-step process that helps development teams efficiently build the highest quality software at the lowest cost. Teams follow the SDLC to help them plan, analyze, design, test, deploy, and maintain software. The SDLC also helps teams ensure that the software meets stakeholder requirements and adheres to their organization’s standards for quality, security, and compliance.

The SDLC includes different phases, and each phase has a specific process and deliverables. Although SDLC meaning might vary for each development team, the most common phases include:

• Requirements gathering and analysis: Business analysts work with stakeholders to determine and document the software requirements.

• System design: Software architects translate the requirements into a software solution and create a high-level design.

• Coding: Developers build the software based on the system design.

• Testing: The software is tested for bugs and defects and to make sure that it meets the requirements. Any issues are fixed until the software is ready for deployment.

• Deployment: The software is released to the production environment where it is installed on the target systems and made available to users.

• Maintenance and support: This ongoing process includes training and supporting users, enhancing the software, monitoring performance, and fixing any bugs or security issues.

SDLC phases and how they work

Each phase of the SDLC has key activities designed to drive efficiently, quality, and customer satisfaction.

Requirements gathering and analysis

Accurate, complete, and measurable user requirements are the foundation for any successful SDLC project—to ensure that the software meets user expectations and to avoid costly rework and project delays. The IT business analyst:

• Gathers requirements by conducting interviews, holding workshops or focus groups, preparing surveys or questionnaires, and observing how stakeholders work.

• Evaluates the requirements as they relate to system feasibility, and software design and testing.

• Models the requirements and records them in a document, such as a user story, software requirements specification, use case document, or process specification.

System design

Effective system design properly accounts for all documented requirements. In this phase, software architects use tools to visualize information about the application’s behavior and structure, including:

• The unified modeling language (UML) to illustrate the software’s architectural blueprints in a diagram.

• Data flow diagrams to visualize system requirements.

• Decision trees and decision tables to help explain complex relationships.

• Simulations to predict how the software will perform.

To support the distinct layers within a software application, software architects use a design principle called separation of concerns. A software program that’s designed to align with the separation of concerns principle is called a modular program.

Modular software design separates program functionality into interchangeable, independent modules, so that each module contains everything it needs to execute one aspect of the software’s functionality. This approach makes it easier to understand, test, maintain, reuse, scale, and refactor code.

Coding

In the coding phase, developers translate the system design specifications into actual code. It’s critical that developers follow best practices for writing clean, maintainable, and efficient code, including:

• Writing code that’s easy to understand and read.

• Using comments to explain what the code does.

• Using version control to track any changes to the codebase.

• Refactoring the code if needed.

• Conducting a code review when coding is completed to get a second opinion on the code.

• Providing code documentation that explains how the code works.

Testing

Before it’s released to production, the software is thoroughly tested for defects and errors.

• The software test plan provides critical information about the testing process, including the strategy, objectives, required resources, deliverables, and criteria for exit or suspension.

• Test case design establishes the criteria for determining if the software is working correctly or not.

• Test execution is the process of running the test to identify any bugs or software defects.

Developers and quality assurance teams use automated testing tools to quickly test software, prepare defect reports, and compare testing results with expected outcomes. Automated testing saves time and money, provides immediate feedback, and helps improve software quality. Automated testing can be used for:

• Unit testing: Developers test the individual software modules to validate that each one is working correctly.

• Integration testing: Developers test how the different modules interact with each other to verify that they work together correctly.

• System testing: Developers test the software to verify that it meets the requirements and works correctly in the production environment.

• User acceptance testing: Stakeholders and users test the software to verify and accept it before it’s deployed to production.

Deployment

There are three main phases to deploying software in a production environment:

• The development team commits the code to a software repository.

• The deployment automation tool triggers a series of tests.

• The software is deployed to production and made available to users.

Effective software installation requires a consistent deployment mechanism and a simple installation structure with minimal file distribution. The team must also make sure that the correct configuration file is copied to the production environment and that the correct network protocols are in place. Before migrating data to the new system, the team also needs to audit the source data and resolve any issues.

Release management makes software deployment smooth and stable. This process is used to plan, design, schedule, test, and deploy the release. Versioning helps ensure the integrity of the production environment when upgrades are deployed.

Maintenance and support

After the software is deployed, the software maintenance lifecycle begins. Software requires ongoing maintenance to ensure that it operates at peak performance. Developers periodically issue software patches to fix bugs in the software and resolve any security issues.

Maintenance activities also include performance monitoring of both the software’s technical performance and how users perceive its performance. Providing training and documentation to users, along with addressing user issues and upgrading their systems to make sure they’re compatible with the new software, are also key components of the software maintenance lifecycle.

What are the SDLC methodologies?

In the world of software development, different methodologies serve as structured approaches to guide the process of creating and delivering software. These methodologies shape how teams plan, execute, and manage their projects, impacting factors such as flexibility, collaboration, and efficiency. Let's take a look at some of the more prominent SDLC methodologies.

Waterfall model

Introduced in 1970, the first SDLC approach to be widely used by development teams is called the waterfall model. This method divides the software development process into sequential phases. Work flows down from one phase to another, like a waterfall, with the outcome of one phase serving as the input for the next phase. The next phase can’t begin until the previous one is completed.

The waterfall model works best for small projects where the requirements are well-defined, and the development team understands the technology. Updating existing software and migrating software to a new platform are examples of scenarios that are well-suited for the waterfall model.

Waterfall model advantages

• The straightforward process is easy to understand and follow.

• An output is delivered at the end of each phase.

• Project milestones and deadlines are clearly defined.

Waterfall model disadvantages

• Lack of flexibility makes it difficult for development teams to adapt when stakeholder requirements change.

• Once a phase is completed, any changes can be costly to implement and might delay the project schedule.

• Testing does not take place until the end of the SDLC.

Agile methodology

The term “agile” describes an approach to software development that emphasizes incremental delivery, team collaboration, and continual planning and learning. Unlike the waterfall model’s sequential process, the agile methodology takes an iterative approach to software development.

Iterative software development speeds the SDLC by completing work in sprints, which are fixed project cycles that typically last between two and four weeks. Key terms include:

• User stories: User stories are short descriptions of product requirements from the customer’s point of view. The most critical user stories are prioritized at the top of each sprint’s backlog of work.

• Increment: The sprint’s output is called the increment. Each increment should be of potentially shippable quality, with all coding, testing, and quality verification completed.

• Retrospectives: At the end of each sprint, the agile team conducts a retrospective meeting to evaluate the process and the tools, discuss what did and didn’t go well, and determine what to improve in future sprints.

The agile methodology is well-suited for projects that require flexibility and the ability to quickly adapt to changing requirements. Because it encourages collaboration, agile is also well-suited for complex projects where many teams work together.

Agile methodology advantages

• Stakeholders and users can provide feedback throughout the SDLC, making it easier for developers to build software that meets their needs.

• Incremental delivery helps development teams identify and fix issues early in the project before they become major problems.

• Cost savings might be realized by reducing the amount of rework required to fix issues.

• Retrospectives provide an opportunity for teams to continuously improve the process.

Agile methodology disadvantages

• Requirements must be clearly defined in the user story. If not, the project can quickly derail.

• Too much user feedback might change the scope of the project, cause delays, or make it difficult to manage.

• Incremental deliverables can make it difficult to determine how long it will take to finish the entire project.

Agile frameworks

Agile methods are often called frameworks and the most common agile framework is called “scrum.” There are the three key roles on the scrum team:

• The scrum master ensures that the team follows the scrum process and is continuously looking for ways that the team can improve while resolving issues that arise during the sprint.

• The product owner takes responsibility for what the team builds and why they build it, along with keeping the backlog of work in priority order and up to date.

• The scrum team members build the product and are responsible for engineering and quality.

The scrum team decides how to manage its own workload for each sprint based on the backlog shown on a task board. Team members participate in a daily scrum (or daily standup) meeting where each person reports on their individual progress. At the end of the sprint, the team demonstrates their potentially shippable increment to stakeholders, conducts a retrospective, and determines actions for the next sprint.

Kanban is another agile framework. Kanban is Japanese term that means billboard or signboard. Kanban boards visualize work items as cards in different states to provides at-a-glance insight into the status of each project and make it easy to identify any bottlenecks.

To help them work most effectively, development teams might adopt aspects of both the scrum and kanban agile frameworks.

Other popular SDLC methodologies

• The iterative model emphasizes continuous feedback and incremental progress. It organizes the development process into small cycles where developers make frequent, incremental changes to continuously learn and avoid costly mistakes. The iterative model is well-suited for large projects that can be divided into smaller pieces, and for projects where the requirements are clearly defined from the start.

• The spiral model combines the iterative and waterfall models. It takes an evolutionary approach where developers iteratively develop, test, and refine the software in successive cycles, or spirals. Large, complex, and costly projects are well-suited for this model.

• The v-shaped model emphasizes testing and validation in a sequential process. This model is very useful for projects in industries like healthcare, where thorough testing is critical.

• The lean model focuses on increasing efficiency throughout the development process. This model takes an iterative approach and is well-suited for projects where achieving short-term goals is a priority and when there’s frequent interaction between the development team and users.

SDLC best practices and challenges

The biggest challenges to a successful SDLC often stem from inadequate communication, planning, testing, or documentation. Best practices to address these issues include:

• Collaboration between the development team, IT operations, the security team, and stakeholders.

• Clearly defining user requirements and project deliverables, timelines, and milestones.

• Detailed documentation of resources, schedules, code, and other deliverables.

• Daily scrum meetings to identify and resolve issues.

• Retrospectives to drive continuous improvement across the SDLC.

SDLC security

Due to increasing cyberattacks and security breaches, development teams are under pressure to improve application security. SDLC security is a set of processes that incorporate robust security measures and testing into the SDLC. Best practices support the detection and remediation of security issues early in the lifecycle—before the software is deployed to production.

How does DevOps work with the SDLC?

DevOps is an approach to SDLC that combines development (dev) and operations (ops) to speed the delivery of quality software. The core principles of this approach are automation, security, and continuous integration and continuous delivery (CI/CD), which combines the SDLC into one integrated workflow.

DevOps follows the lean and agile SDLC methodologies and emphasizes collaboration. Throughout the entire SDLC, developers, IT operations staff, and security teams regularly communicate and work together to ensure successful project delivery.

See a comparison of DevOps solutions

Conclusion

A well-structured SDLC helps development teams deliver high-quality software faster and more efficiently. Although SDLC methods vary by organization, most development teams use SDLC to guide their projects.

The SDLC helps development teams build software that meets user requirements and is well-tested, highly secure, and production ready. Popular tools that support the SDLC process include:

• GitHub Actions to automate SDLC workflows.

• GitHub security tools to help developers ship secure applications.

• GitHub Copilot to developers write code faster with AI.

• GitHub code review tools to help avoid human error.