SDLC models define how the phases of software development — requirements, design, implementation, testing, deployment, maintenance — are organized. The choice of model directly impacts project risk, delivery speed, quality, and team structure.
Classification of Models
| Category | Models | Key trait |
|---|---|---|
| Traditional (Linear) | Waterfall, Iterative Waterfall, V-Model | Sequential phases, heavy documentation |
| Iterative & Risk-Driven | Prototype, Spiral, Incremental | Repeated cycles, early feedback |
| Agile | Scrum, XP, Kanban | Short iterations, customer collaboration |
| Speed-Focused | RAD | Rapid prototyping, automated tools |
| Modern | DevOps | Development + Operations merged |
What Interviewers Ask
The most common SE interview question is: “Which model would you choose for Project X?” There’s no single right answer — they want to hear your reasoning. Consider:
- Are requirements well-understood? → Waterfall or V-Model
- Are requirements vague? → Agile or Prototype
- Is the project high-risk? → Spiral
- Is time-to-market critical? → RAD or Agile
Q: Can you use multiple models in one project?
A: Yes. A common hybrid is Waterfall for the planning/requirements phase (which needs stability) and Agile for construction (which benefits from iteration). This is called a “hybrid model.”
Q: What’s the most popular model today?
A: Scrum (an Agile framework) is the most widely used. But most teams adapt it — pure Scrum is rare. DevOps practices overlay on top of whatever development model you use.
Q: Which model has the least documentation overhead?
A: Kanban and XP. Kanban uses a simple board; XP emphasizes code and tests over documents. But “less documentation” can become a maintenance liability later.
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