The strategy for breaking down and delivering work can significantly impact the overall success and efficiency of a project. Traditionally, many teams have used a horizontal slicing method, completing project layers such as database, API, and front-end sequentially. However, this approach often delays the delivery of usable features and hinders early testing and feedback. We must shift towards vertical slicing, a method that permits enhanced collaboration, faster delivery, and better alignment with agile methodologies.
Understanding Horizontal vs. Vertical Slicing
Horizontal Slicing
Definition: Horizontal slicing involves completing all tasks related to one layer of the technology stack before moving on to the next.
Disadvantages:
- Delays in delivering usable features: No single layer constitutes a deliverable that provides value on its own.
- Increased risk due to late integration: delayed integration, will lead to delayed discovery of issues/challenges towards the end of a project.
- Challenges in early testing and validation, as the functionality can only be tested once all layers are complete.
Vertical Slicing
Definition: Vertical slicing means breaking down the project into smaller, functional increments that span all necessary layers to deliver a working feature.
Advantages:
- Early and Continuous Delivery: Allows for the incremental release of functional enhancements to the customer, facilitating continuous improvement and adaptation.
- Immediate Feedback: Each slice is a testable and deliverable feature, enabling real-time user feedback and hypothesis testing.
- Cross-Disciplinary Collaboration: Encourages involvement from all disciplines (e.g., backend, frontend, UX) from the start, fostering a better understanding and more cohesive development process.
The Benefits of Vertical Slicing
Iterative Delivery and Feedback:
- Vertical slicing aligns perfectly with agile principles, supporting iterative development and frequent reassessment of project priorities based on stakeholder feedback.
- Examples of iterative delivery can include releasing a basic login page followed by incremental additions such as multi-factor authentication or social login capabilities.
- By involving various team members in each slice, vertical slicing breaks down silos and promotes a unified approach to problem-solving.
- This collaboration can lead to more innovative solutions that are closely aligned with user needs and expectations.
- Early detection of potential issues (i.e. api design) and continuous testing reduce the likelihood of major setbacks, as adjustments can be made promptly without disrupting the entire project.
Implementing Vertical Slicing in Your Projects
Identifying Vertical Slices:
- Focus on delivering small increments that each add user value. Begin with the core functionality and enhance with additional features in subsequent iterations.
- Ensure each slice is independently deployable, even if it's a minimal implementation of the feature.
- Horizontal Approach: A project is divided into separate phases where the database models are developed first, followed by the business logic, then the API, and finally the front-end.
- Vertical Approach: The project starts with a single feature, such as user registration, which includes database setup, business logic, API, and front-end in the first slice. This feature is fully functional and can immediately be used and tested.
Vertical slicing offers numerous advantages over traditional horizontal slicing by aligning project delivery with agile principles of iterative development, rapid feedback, and cross-functional collaboration. By adopting vertical slicing, teams can not only accelerate their delivery timelines but also enhance product quality and stakeholder satisfaction.