Waterfall is a sequential, plan-driven approach: gather all requirements, design, build, test, then release — each phase finishing before the next begins. Agile is iterative and adaptive: deliver small working slices repeatedly and adjust based on feedback. Neither is universally "better"; they fit different contexts.
Side by side
| Aspect | Waterfall | Agile |
|---|---|---|
| Approach | Sequential phases | Iterative increments |
| Requirements | Fixed upfront | Evolve over time |
| Feedback | Late (after build) | Continuous |
| Risk | Surfaces at the end | Surfaces early |
| Working software | Delivered once | Every iteration |
| Best for | Stable, well-known scope | Uncertain, changing scope |
Concrete example
Building a regulated payroll system with fixed legal rules may suit Waterfall's upfront rigor. Building a new consumer app where you don't yet know what users want strongly favors Agile's fast feedback.
Common pitfalls
- Claiming Agile is always superior — fixed-scope, high-compliance work can favor plan-driven methods.
- "Water-Scrum-fall": Agile labels on a fundamentally sequential process.
- Using Agile as an excuse for no planning at all.
Why it matters
Choosing the right approach depends on uncertainty: the less you know upfront, the more Agile's short feedback loops pay off.
Interviewers want to see nuanced judgment, not dogma — the ability to pick the method that fits the problem.