Agile SDLC and the traditional Waterfall model differ mainly in how work is planned, executed, and adapted to change. Here’s a clear, side-by-side explanation.
1. Core Philosophy
Waterfall
- Linear and sequential
- Each phase must be completed before the next begins
- Assumes requirements are fixed and well understood upfront
Agile
- Iterative and incremental
- Work is done in small cycles (sprints)
- Assumes requirements will evolve over time
2. Development Flow
Waterfall Flow
- Requirements
- Design
- Development
- Testing
- Deployment
- Maintenance
- No going back easily once a phase is finished
Agile Flow
- Plan → Build → Test → Review → Improve (repeats every sprint)
- Continuous feedback and improvement
3. Requirements Handling
Waterfall
- All requirements defined at the start
- Changes are costly and difficult later
Agile
- Requirements evolve through the project
- Changes are welcomed, even late in development
4. Customer Involvement
Waterfall
- Limited involvement after requirements phase
- Customer sees the product near the end
Agile
- Continuous customer collaboration
- Frequent demos and feedback after each sprint
5. Testing Approach
Waterfall
- Testing happens after development is completed
- Bugs discovered late in the cycle
Agile
- Testing is continuous and integrated into each sprint
- Issues are detected and fixed early
6. Delivery
Waterfall
- Single final delivery at the end of the project
Agile
- Frequent, incremental releases of working software
7. Risk Management
Waterfall
- High risk if requirements are misunderstood
- Problems surface late
Agile
- Lower risk due to early feedback and frequent releases
- Issues identified early
8. Documentation
Waterfall
- Heavy documentation upfront
- Documentation drives development
Agile
- Lightweight, just-enough documentation
- Working software is the primary measure of progress
9. Team Structure
Waterfall
- Specialized roles (analyst, developer, tester)
- Handoffs between phases
Agile
- Cross-functional, self-organizing teams
- Collaboration over handoffs
10. Comparison Summary
| Aspect | Waterfall | Agile |
|---|---|---|
| Process | Sequential | Iterative |
| Flexibility | Low | High |
| Change Cost | High | Low |
| Customer Feedback | Late | Continuous |
| Testing | After development | Throughout |
| Delivery | One-time | Frequent |
When to Use Which?
Use Waterfall when
- Requirements are stable and well-defined
- Regulatory or compliance-heavy projects
- Small, low-uncertainty projects
Use Agile when
- Requirements are changing or unclear
- Need fast time-to-market
- Customer feedback is critical
