Waterfall Vs. Agile Vs. DevOps Vs. Lean


The IT industry has witnessed tremendous changes over a decade or so, with the continuous evolution of technologies as well as methodologies. More than simply developing and deploying a one-time solution, the focus has shifted towards a continuous integration and deployment approach. There is a constant need for upgrading and integrating the solution with the existing software to meet the market demands.

Therefore, owing to a continuous delivery approach, the communication between stakeholders involved in developing a software solution and the end-users has increased more than ever, due to which there is a constant need for feedback and its implementation. SDLC began with Waterfall but is gradually shifting to other models and finally approaching the agile DevOps and Lean methodologies.

Waterfall model

This model is a traditional methodology and a first-of-its-kind software development model that follows a linear software development approach. Each phase in the waterfall model is completed before it moves on to the next phase. In the sequential type of software development, each phase is distinct and has to be very clear from the very beginning. The phases begin with requirement gathering followed by analysis, design, coding, testing, and deployment.

Due to its rigid nature of development, as one cannot go back to the previous phase to make any change, the model gradually became obsolete with the emergence of the dynamic nature of the software development process, where there needs to be a constant change in implementation, as per the user feedback, to keep up with the changing needs of the IT industry.

Let us look at the few modern software development models extensively followed in today’s industry.

Lean Methodology

The concept of lean software development derived its existence in the IT industry from Toyota manufacturing, as Toyota production system was the first company to introduce the lean development process in the mid 20th century to improve their car production and eliminate wastage of time and resources.

Many manufacturing sectors, across various industries, followed this approach, which was first implemented in software development in 2003.

Why Lean in software?

There are various reasons for the popularity of Lean methodology in the IT industry, such as it allows frequent product changes and software releases, shorter development life-cycle, seamless exchange of preliminary development steps, simultaneous improvement in development quality and time, etc.

These are some of the noteworthy factors that make the lean development model crucial for organizations that want to keep up with the current pace of software development.


Agile is a continuous integration and deployment approach which is iterative in nature. It derives its principles from Lean methodology. Some of the agile approaches can be attributed to the following concepts:

  • Frequent analysis and implementation of changes.
  • Team-oriented leadership or precisely ownership of tasks, by each member of the team.
  • Is usually very self-organized and accountable for its deliverables.
  • Agile seamlessly aligns organizational and customer expectations.

Agile Process:

Following are the various processes that are used to implement agile -

  • Scrum - this process of agile development focuses on a team-driven development environment. The team is composed of 7 to 9 members, usually, with major roles and responsibilities classified as a scrum master, product owner, and scrum team. The three roles can be elaborated further as follows:
    1. Scrum master - this member is responsible for organizing the team and eliminating Communication gaps or any other gap pertaining to the task being delivered.
    2. Product owner - this member is responsible for creating a product backlog, prioritizing the backlog, and ensuring that the designated tasks are completed by the end of each iteration.
    3. Scrum team - the team is responsible for completing the allocated tasks within a sprint, by a self-organized and collaborative approach.

    Some of the scrum practices are listed as follows:

    • Sprint planning - in this type of planning the team discusses the product backlog, initial plan of action, and the tasks to be completed during this sprint.
    • Daily scrum meets - daily scrum meetings refer to the daily morning meetings, usually time-boxed for 15 minutes, where they discuss their plan of action for the day.
    • Sprint review meeting - this type of review meeting refers to a meet where completion of the planned course of action is discussed and monitored to determine the future course of actions needed to accomplish any bottlenecks.
    • Sprint retrospective meets - this is the last phase and the last scrum meeting where the overall development strategies are discussed concerning the scope of solution implementation, identification of bottlenecks, the success of planned courses, and any other scope of improvement, which could be adopted in future projects, are discussed.
  • Crystal methodologies - This methodology emphasizes the interaction between people, more than processes and tools. This method emphasizes the approaches adopted by the team according to the scope of a project.
  • Dynamic Software Development Method (DSDM) - this methodology is also referred to as a rapid action development model, wherein the users are involved actively in the development of the project. Teams are empowered with decision-making capabilities.
  • Feature-driven development (FDD) - this is a feature-driven methodology, where each phase involves completing a small feature within the given time. It consists of design walk-through and code inspection, and so on.
  • Lean software development - Lean software development encompasses ‘just in time’ production techniques. This methodology aims to eliminate waste, reduce cost, thereby increasing the efficiency of the entire software development process.
  • Extreme programming (XP) - Extreme programming methodology is very useful in scenarios where there are frequent release cycles, shorter development phases, and uncertainties relating to the functionality to be developed.


This terminology emerged from the term's development and operations respectively. DevOps emphasizes the constant collaboration and communication between the teams to ensure a seamless development process. The various phases in the DevOps life cycle are focused on constantly monitoring, operating, implementing, and responding to the end-user feedback to ensure continuous integration and deployment.

Following are the phases in the DevOps life cycle:

  • Continuous development - this phase consists of planning and coding activities. Planning involves the overall vision of the project and lists the activities to be performed as per the plan of action.
  • Continuous integration - this phase comprises of integrating code changes as per any added functionality. This phase helps detect bugs at the earliest, with the help of unit testing tools, code review, integration testing, and so on.
  • Continuous testing - a phase that involves continuous testing of the developed software. The testing is usually carried out with the help of automation tools to save time and effort.
  • Continuous feedback - in a beta testing environment, the users of the application provide their valuable feedback on the performance of the application, followed by implementation of those by the developers.
  • Continuous monitoring - Monitoring the performance of the application is a crucial step towards building efficiently performing software. Often issues like memory leakage, server not found, and more are a common phenomenon, which needs to be dealt with regularly.
  • Continuous deployment - each time a change has to take place, the software needs to be updated to incorporate the newly added functionality. Once a code is released, the same gets uploaded on the server, which takes care of the updates on individual devices. The continuous deployment process is accomplished with the help of the Configuration Management process which uses containerization tools to implement updates.
  • Continuous operations - this phase is about maintaining consistency in updating the changes with every new release.

The DevOps life cycle focuses on efficiently bridging the gap between the tools, processes, and capabilities.

Agile VS Waterfall vs DevOps vs Lean - Key differences and similarities

Although by now we understand the correlations and similarities between the four terminologies mentioned in the article, we have still attempted to list down these differences as well as similarities for a more comprehensive understanding.

Agile vs Waterfall

  • Agile follows an iterative approach, whereas waterfall is a step-by-step approach.
  • Agile is based on continuous feedback and implementation, whereas in waterfall it is not possible to go back to a previous step after we have moved on to the consecutive step.
  • Delivery of a project in agile is faster, whereas the waterfall model is quite time-boxed and rigid in terms of completion of each phase of the software development life-cycle.
  • Agile comprises multiple projects, whereas waterfall is fixated on a single project.
  • In agile, test plans are reviewed in each sprint, whereas in waterfall test plans are hardly reviewed.
  • Requirements can be modified as per changing requirements in agile, whereas waterfall does not allow frequent changes.

Agile vs Lean

Agile inherits its underlying meaning from Lean practices of process implementation. Therefore, there is no substantial difference between the two, as both the methodologies emphasize time-saving and cost reduction through continuous implementation, eliminating unnecessary development.

Agile vs DevOps

  • DevOps emphasizes collaboration between development and operations teams, whereas agile is simply an iterative model that aims to continuously integrate and deploy software releases.
  • A significant area of focus in DevOps is continuous testing and deployment, whereas a trial is aimed at catering to continuously changing requirements.
  • DevOps often involves a very large team, whereas agile is usually comprised of smaller teams.
  • Agile phases are comprised of scrums, sprint planning, sprint review, etc. DevOps on the other hand includes planning, building, continuous delivery, testing, and feedback.
  • Agile is a software development approach, whereas DevOps is about end-to-end solution delivery.


There are various methodologies and approaches for software development, however not all methodologies are used in every organization. The adoption of a strategy and technique largely depends on the type of projects a company has, the kind of audience it caters to, and various other factors that form the foundation for the selection of a certain type of methodology.