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SDLC Models in Action

Inna Levchenko

How do development companies turn wild ideas into full-fledged applications? At a glance, all that has been done before software delivery looks magically: you’ve discussed requirements with a project manager, then hammered out some details on and off, and “Wow, the app is done perfectly”. It’s easy to guess that the development process takes place in the exact sequence. In this article, I shed the light on this magic which software gets passed from the ideation phase to delivery, provides insight on the most common types, and compares to make your choice effortless.

What is SDLC?

To deliver the qualitative product both on time and on budget, the engineers should adhere to distinct stages. The software development life cycle is a defined process for software development that ensures that the project will meet customers' expectations. SDLC consists of well-planned steps that explain how to create the specified product. These phases might vary depending on the business goals, timeframes, and client’s expectations. Eventually, you end up choosing the SDLC model which will lead your project towards established goals as fast, efficiently, and effectively as possible.

Lifecycle stages

Each SDLC model divides into particular parts. Despite the chosen methodology, every phase has its process, which has to be reviewed and tested. Only in this way can the client feel certain of the project's success.

SDLC stages


Mostly, vendors point out the 8 phases of SDLC starting with the planning and ending with the maintenance. Let’s review them in-depth: 

  • Kickoff. Before choosing the model, the development team ought to gather information from all stakeholders, including product owners, involved industry experts, salespeople, and service providers. The main goal for this stage is to understand who will use the system and how this system has to work, then find out the scope of challenges and determine solutions. 

  • Requirements gathering. This phase is the most critical for planning and the project’s success. Every suggestion and expectation need to be fleshed out point by point to provide correct information to developers about a future software product. In simple terms, this means taking a look at the technical stack, number of developers, resource costs, time-frames, and potential risks related to the chosen development cycle.

  • Feasibility analysis. Once the planning stage is finished the next stage is to perform a detailed analysis of business requirements. This means all technical details and their implementation might be defined and documented. Such requirements have to show the development team what the system must look like regarding business needs and tech feasibility. 

  • Design and prototyping. The design phase is divided into the next steps: data structure, database design, creating of layouts, and rapid prototyping. Here, developers analyze and design solid product architecture to prevent a crash, bugs, or lack of performance. If you doubt the validity of the system model, don’t move on to the coding stage. There’s no room for mistakes since those might cost overrun for contractors.

  • Development. It’s about time to start writing the code. At this step, the vendor put on to create the product with a team of programmers. Development takes considerable time, and therefore all projects are split into tasks, which are assigned to every coder. The result of this stage is functional software based on a given specification.

  • Testing. If the product looks as documentation requires, it doesn’t ensure this one meets the final user’s expectations. To build bug-free software, designated testers have to verify the functionality. The acceptance results are achieved by checking the whole system for defects, bugs, errors. Normally, the testing process repeats several times till development, and the Q & A team builds the quality product. 

  • Release. As soon as the testing is crowned with success, the software can deliver to end-users. This process runs by packaging and deploying to the server. All components, data, and software architecture have to run smoothly, as it was developed. Usually, the software is launched by DevOps engineers, who bridge the gap between hardware and software. The output of realizing phase is the working product delivered to final users.

  • Maintenance. To develop a product you ought to follow previous steps but to create the long-living one you have to keep the software operational. Maintenance and support are preferable for every company for several reasons. Firstly, technologies always forge ahead, and you need to make your product faster, more user-friendly, and more functional to stay competitive. Secondly, you can’t develop a once-for-all-time app without bugs: even the greatest tester can make minor mistakes, which will be observed under realistic conditions only. The result of this stage is that your customers feel your focus on quality and responsiveness.

Traditional SDLC Models

There are numerous SDLC models. Some of them might be used by loads of software companies but a far greater number of various models is suitable for particular projects only. Let’s look at the traditional (Waterfall-like) development process, for starters. 


The first known model in software development was Waterfall. Nevertheless, it’s one of the hassle-free approaches, which is relevant so far. The bottom line is that all phases occur in a certain order. In Waterfall, the overlapping of stages isn’t acceptable - you have to finish doing previous actions before you’ll proceed with the next ones. Besides, you can’t return to the stage which was above.

Waterfall development model
The advantage of such rigidity is that the product won’t hold in delay, and the management is easy to understand. However, the same strict order of phase implementation isn’t a good choice for complex long-term projects.


Implementation of the Iterative (Incremental) model isn’t much different from Waterfall. Starting from requirements, the development team goes through the same stages but they aren't supposed to create a product on the first try. During the first iteration, they have to develop a viable product with minimum requirements and functionality. Once the test stage is finished, the team proceeds with the implementation of more complex features. Guess what will happen after the tests? 

Iterative development model

Nevertheless, the process always comes to an end. The last iteration implies realization and maintenance. The bright side of the incremental model is that all requirements are determined at the beginning. Hence, it’s a good choice for long-term projects but unsuitable for small ones. 


Once in a while, everyone in the project demands more tests. That’s why the verification & validation model exists. Here, all stages similarly take place with the previous two. The trick is that every phase needs acceptance and testing to proceed with the next step. 

V-shaped development model

Back in the old days, engineers carried out tests after the design and coding. Nowadays everyone tends to use a test-driven development approach, and hence, all tests got used to being written before. Did it impact the V-model? Obviously, but it is likely to have a positive impact because of prevention from mistakes in the phases of development. The pitfalls of the model are that you have to be sure your requirement is stable and complete in advance. Thus, the model isn’t a great choice for huge projects, where documentation might be flexible.


“So what am I supposed to do with middle-, long-term or just complex projects?” you ask. Everything there is a season, and now’s the time to describe the Spiral model, which is good for those objectives.


Spiral development model

This model is a mix of Waterfall and Iterative models. As soon as the engineers get the requirements, they’ll build the prototype. Then, the next iteration is the creation of new requirements, rather than analysis. Such an order of phases is necessary since the focus of spiral morel is to reduce risks by listening to a client or his end-user. It’s not difficult to understand that this method of SDLC demands more cost as long as the number of iterations might be countless. 


The crux of Agile practice is the product development divides into iterations (sprints), which usually takes a few weeks. Over every sprint, the team can get through the SDLC cycle, from planning to delivery of potential software. Meanwhile, Agile implies daily meetings between shareholders - so they are more flexible for changes during the sprint. Quite simply, the analyzing stage is taking place on a day-to-day basis.


Agile development model

This flexibility allows using the Agile for both short- and long-term projects. The main disadvantage you might be faced with is that the final product won’t meet your origin requirements. On the other hand, if you don’t have strict specifications, the product will satisfy you anyway. Finally, the thing about Agile is that its emphasis is placed on design and development, rather than planning.

 Nontraditional SDLC Models

At times, the development process doesn’t require progress through a full-on SDLC, or even similar processes are meaningless. Those projects are alike by a certain factor - they have a relatively short duration. Even so, the popularity of nontraditional models has left us no choice other than to share the key principles of their use. 

Big Bang

The conditions for the first model are simple: you need a product; you need it within budget and time; no one will test the code quality or modify the part of this in the future. Mostly, the project is developed by one or several engineers who cooperate. In doing so, the client isn’t involved in the development process. All he cares about is the design and functionality of the end product.

BigBang development model

There are pros and cons of using the big bang model. On the one hand, you use simple models, and it gives more flexibility to developers. On the other hand, this model is uncertain and poor for complex projects. Plus, if the coder misunderstood the idea, this product will turn into expensive but useless software. 

Rapid App Development

Although RAD is akin to the iterative model, this approach has its scope of application. More specifically, this development model is a perfect solution for huge forward-going products. Given that successful companies can't afford to rely on luck, they usually build particular features as specific modules. This provides a guarantee that their product won’t go to crash even if developers or business analytics make mistakes in the planning phase. 


RAD development model

Again, the advantage is that you can back up to the previous app version at any time, and your main range of users won’t suspect that something went wrong. The disadvantage is that this development model requires qualified engineers, who won’t mess up the core software functionality. Hence, the RAD model isn’t cheap to be entitled simply “experimental development” or whatever.

 Software Prototype

For the finale, let’s talk about the prototype. The purpose of this model is to demonstrate either to the client or to investors how the product will work in practice. Accordingly, a development flow involves creating the functional software without a complete user interface, minor features, and exact behavior of the original product.


Software propotype development model

Prototyping isn’t so simple as it may seem. The model of the product has to be developed by strict requirements to understand whether the system will work correctly or it should be modified further. Thus, as soon as the team obtains feedback, they must rebuild the prototype following the suggestions. The total cost of building the prototype is unpredictable, and it varies according to the project complexity. Still, it reduces potential risks of failure which will cost more, which explains the importance of the prototype model.

How to pick 

A “one-size-fits-all” model doesn’t exist. Each one has its strengths and weaknesses. The point is, you should take cognizance of your product’s aspects only. There’s no right or wrong methodology but there are loads of unsuitable ones for you. For instance, the development of a landing page differs from the creation of an enterprise app. 


SDLC models in comparison

As you see, the models vary by your willingness to take risks, budget, the expertise of the available staff, project, and business type. These factors have a great deal of project management wherever you set up new software or merely need to maintain the released one.