🚩 SDLC (Software Development Life Cycle): Complete and Detailed Guide with Examples

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The software development life cycle, known as the SDLC (Software Development Life Cycle), is a structured process that guides the development of an application from the birth of the idea to post-release maintenance. A thorough understanding of each phase of the SDLC is essential to ensuring the quality, efficiency, and success of the project.

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🔍 What is the SDLC?

The acronym SDLC stands for Software Development Life Cycle. It is a conceptual and organizational model that describes in detail all the phases involved in software development, from the conception of the idea to its post-release maintenance.

This cycle helps organizations:

  • Plan development strategically

  • Control costs and schedules

  • Ensure quality and user satisfaction

  • Mitigate risks


🧩 SDLC Phases

1. 📒 Planning

The planning phase is the foundation of the project. In this phase, preliminary information is gathered to understand what you want to achieve, why, and how. The project scope is defined, costs, time, resources, and risks are evaluated.

A feasibility analysis is often performed, which covers several aspects:

  • Technical: Is the project technologically feasible?

  • Economic: Do the benefits outweigh the costs?

  • Operational: Is the organization ready to adopt it?

  • Legal: Are there regulatory constraints?

This phase involves figures such as the project manager, stakeholders, business analyst, and in some cases even end users.

✅ Activities:

  • Feasibility Analysis (Technical, Economic, Legal, Operational)

  • Stakeholder Definition

  • Resource and Time Planning

📌 Example:

A company decides to create a food ordering app. In the planning phase:

  • Costs and schedules are estimated (€50,000 and 6 months)

  • Resources are assigned: project manager, developers, designers

  • There is an expected risk of delivery delays from partner restaurants.


2. 🧑‍💼 Requirements Analysis

Here we enter the analytic phase. The team must fully understand what they want to build. This includes both functional requirements (functionality the software must offer) and non-functional requirements (performance, security, usability, scalability).

Requirements gathering can be done through:

  • Interviews with users/stakeholders

  • Questionnaires

  • Business process analysis

  • Study of competing software

The result is a formal document called the SRS (Software Requirements Specification), which serves as a guide for all subsequent phases.

✅ Activities:

  • User interviews

  • Functional/Non-Functional Requirements Documentation

  • Creating the SRS

📌 Example:

For the food delivery app:

  • Functional requirement: "The user can order food from the restaurant selected"

  • Non-functional requirement: "The system must respond within 2 seconds even with 500 active users."


3. 🎢 Design

During this phase, the team transforms the requirements into technical and architectural specifications. This includes:

  • Technology selection (e.g., React, Python, PostgreSQL)

  • System architecture design (monolithic, microservices, client-server, etc.)

  • Data modeling (database schema)

  • Defining the User Interface (UI/UX)

Deliverables include technical documents, UML diagrams, interface prototypes (wireframes), and often proofs of concept.

✅ Activities:

  • Architecture Design

  • Technology Selection

  • UI/UX and wireframe

📌 Example:

  • You choose a REST architecture with React Native for the mobile app

  • Endpoints are defined as: /api/menu, /api/order

  • Wireframe: home screen, restaurant list, dish detail


4. 👩‍💻 Implementation (Development)

It is the phase in which The code is written. Developers follow the design specifications to achieve the intended functionality.

Development can follow different strategies:

  • Incremental Development (feature by feature)

  • TDD (Test Driven Development)

  • CI/CD (Continuous Integration and Deployment)

Large teams use collaboration and versioning tools such as Git, GitHub, Jira, Docker, etc.

✅ Activities:

  • Coding features

  • Source code management

  • Integration between modules

📌 Example:

Developers implement:

  • User login with Firebase

  • Backend with Node.js

  • Payment gateway integration Stripe


5. 🕵️‍♀️ Testing

Objective: Ensure that the software works correctly, is bug-free, and meets requirements. It is essential to test both system behavior and performance.

Test Types:

  • Unit Tests: Tests individual functions/methods

  • Integration Tests: Tests the interaction between modules

  • System test: verification of the complete system

  • User Acceptance Test (UAT): verification by users

  • Stress Testing / Load Testing: Testing under extreme conditions

Detected bugs are documented and fixed before being released for production.

✅ Activities:

  • Functional Testing

  • Automated/Manual Testing

  • Bug Fix

📌 Example:

  • QA tests payment under slow network conditions

  • A bug is identified in the cart: the total doesn't update if a dish is removed.


6. 🚀 Deployment

Once the software has been tested and approved, it is released to production. Depending on the project, deployment can be:

  • Manual

  • Automatic (CI/CD)

  • Gradual (canary release, A/B testing)

The following must be set up:

  • Production and staging environments

  • Data backup

  • Rollback mechanisms

✅ Activities:

  • Software release

  • Post-deployment monitoring

  • Server configuration and security

📌 Example:

  • The app is published on Google Play and the App Store

  • Crash and performance monitoring using tools like Firebase Crashlytics


7. 🐞 Maintenance

This phase continues for the entire useful life of the software. Includes:

  • Fixes for bugs discovered after release

  • Compatibility updates (new OS, browsers)

  • New features based on user feedback

  • Security Patches

Maintenance can be corrective, adaptive, enhancing, or preventive.

✅ Activities:

  • Managing User Reports

  • Updates and Patches

  • Software Extensions

📌 Example:

The company receives reports of accessibility issues for the visually impaired. The UI is improved and screen reader support is added.


📚 SDLC Models

Before applying the Software Development Life Cycle, it's important to choose the right development model—a strategic framework that defines how and when each SDLC phase is executed. The choice depends on the type of project, level of flexibility required, stakeholder involvement, and risk tolerance.

Each model offers distinct advantages and trade-offs in terms of planning, adaptability, cost, and delivery speed. Below, we explore the three most widely used SDLC models: Waterfall, Iterative-Incremental, and Agile—detailing when and why to use each.

1. Waterfall Model

This is the most traditional model. The phases follow one another in a linear and sequential way: one phase must be completed before moving on to the next. There is no provision for reverting to previous phases.

Pros:

  • Simple and clear structure

  • Ideal for projects with well-defined requirements


Cons:
  • No flexibility for changes

  • Expensive to correct errors late in the process

 

2. Iterative-Incremental Model

Software is developed in small increments, each of which adds functionality. Each iteration includes a mini-version of the complete cycle (analysis, development, testing).

Pros:

  • Frequent deliveries and continuous feedback

  • Reduces the risk of total failure
Cons:
  • Requires good initial planning

  • Can complicate management project

 

3. Agile Model

Agile is a philosophy, not a rigid process. It promotes continuous collaboration, short sprints, adaptability, and frequent delivery of working software. The most well-known frameworks are Scrum, Kanban, Extreme Programming (XP).

Pros:
  • High flexibility and adaptability to change

  • Direct customer involvement
Cons:
  • Requires disciplined teams

  • Not suitable for projects with fixed requirements and a rigid budget

 

✅ Conclusion

The SDLC is an essential component for structured and professional software development. Its phases – from planning to maintenance – help control every aspect of the project, reducing errors and increasing final value.

The choice of SDLC model (Waterfall, Iterative, Agile) must be consistent with:

  • Project type

  • Available resources

  • Degree of uncertainty

  • Quality requirements


Criterion / Type of Project Waterfall Iterative-Incremental Agile
RequirementsWell-defined and stable projects ✅ Yes ✅ Yes ⚠️ Not ideal
Small, low-risk projects ✅ Yes ✅ Yes ✅ Yes
Projects with high uncertainty about requirements ❌ No ✅ Yes ✅ Perfect
Need frequent feedback from users/customers ❌ No ✅ Partial ✅ Yes
Short time-to-market / fast delivery ❌ No ✅ Possible ✅ Excellent
Fixed budget and timeframe, documentation required in advance ✅ Ideal ⚠️ Depends ❌ Critical
Large-scale projects, independent modules ⚠️ Complex ✅ Yes ✅ With Scrum
Distributed or poorly communicated team ✅ Yes ✅ Yes ❌ Not recommended
High priority on software quality from the beginning ⚠️ Complex ✅ Yes ✅ Yes
Customers willing to actively and continuously collaborate ❌ No ✅ Gradual ✅ Critical



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