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Agile vs Waterfall: Key Differences

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Sujith G
Agile vs Waterfall Key Differences
Table of Contents

Any project involves Planning, Doing, Checking, and Acting/Adjusting as part of the delivery (the all-familiar PDCA). We start with requirement gathering, move to planning followed by designing, and then proceed with development, testing, and deployment in that order. These are the basic steps involved in the development of software or basic steps to follow for completing any project with minor tweaks here and there. We were doing these steps sequentially with big upfront planning for decades with great success till the time the business landscape changed dramatically with constant customer requirement changes, technological advancement, and the maturing of the software industry.

Over time with evolution in the ways of working, there was a significant improvement in the way we deliver the projects. Just enough planning with shorter feedback cycles and continuous PDCA with iterative and incremental software development or Agile in short became the norm for delivering most products/projects. Though, even now, both Waterfall and Agile continue to be the two of the most popular software development life cycle (SDLC) frameworks that the software industry uses to deliver projects.

In the world of software development, choosing the right methodology can make a significant difference between project success and failure. Both these approaches have dominated the industry for years. There are pros and cons with both the agile and waterfall approaches though the industry based on the current time and need is moving towards Agile.

That leaves us with age-old questions:

  1. “Agile vs Waterfall” Which one is better and what suits us best?
  2. What should my teams prefer in agile methodology vs waterfall?
  3. How to choose between agile versus waterfall?
  4. What is the difference between agile and waterfall methodology?
  5. Can you follow both waterfall and agile methodologies?
  6. What are waterfall methodology and agile methodology?

This blog aims to answer the question backed with some literature on both methods explaining the:

  1. Pros and cons of both waterfall and agile methodologies
  2. How are agile vs waterfall different?
  3. How are agile and waterfall methodologies executed?

Agile Vs. Waterfall – Key Differences

Pillar Agile Waterfall
Approach Iterative and incremental development Sequential and linear development
Flexibility Emphasizes flexibility and adaptability to change Less flexible, changes are difficult to accommodate
Requirements Requirements evolve and can be adjusted Requirements are defined upfront and difficult to change
Planning Short-term planning with room for adjustments Extensive upfront planning with limited flexibility
Phases No fixed phases; work happens in iterations Fixed phases (requirements, design, development, testing)
Feedback Continuous feedback throughout the project Feedback usually comes late in the project
Risk Management Risks identified and mitigated early Risks addressed sequentially, often late
Client Involvement Frequent client collaboration and feedback Client involvement mainly at start and end
Time-to-Market Faster delivery through incremental releases Longer time-to-market due to sequential flow
Documentation Focus on working software over documentation Comprehensive documentation at every stage
Quality Left-shifted quality with continuous testing Testing is a separate phase after development
Team Work Culture Pull system – teams pull work themselves Manager assigns work to team members
Decision Management Decentralized decision-making Centralized decision-maker
Responsibility Team succeeds or fails together Manager is usually held responsible

What is the Waterfall methodology?

Waterfall is a simple SDLC model that involves breaking the project into phases and then executing the phases sequentially with gates and reviews to proceed to the next phase. These phases usually include:

  1. Planning everything in detail with specs and getting it signed off
  2. Designing the architecture and UI and confirming with a sign-off
  3. Developing entire application
  4. Testing the entire application
  5. Deploying the whole application at once
  6. Maintenance and support

This model highly promotes knowing everything about the project well in advance, sign off before we move to the next phase and documentation of everything in all the phases. Any change needed would have to go through the entire flow from the start. The customer or the user would get the product at the end of the project tenure.

Just like a waterfall, the progress of the project is in one direction, that is, once teams move onto a new phase, they are not allowed to revisit a previous one. The picture below shows the flow of progress in a typical waterfall project

Waterfall methodology project

Advantages

The Waterfall model was the most used SDLC method in the industry and the reason for its popularity and widespread usage was that the companies saw its fitment to deliver projects. Here are a few advantages of waterfall:

  1. One of the main advantages of the waterfall model is its clarity and concrete structure, which sets expectations with each role in the team on the job to be done at every phase of the project
  2. Since the waterfall model cannot progress to the next phase without the previous phase being completed, information is always recorded properly from one phase to another
  3. It is the simplest execution to manage as the phases, exit, and entry criteria are clearly defined
  4. Reduces surprises for the stakeholders as every phase is signed off by them

Limitations

Time has become a critical factor in delivering a product, that is if you delay in delivering a critical feature, your competitor has already taken a portion of your market. And with evolving technology and changing customer requirements, your delivery methods have to be flexible and will have to iterate over a plan not waiting for a long time to deliver something. Here are a few disadvantages with waterfall: