How does Agile compare to Waterfall?

Question

IT Interview Practice · Accepted Answer

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.

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

Side by side

Concrete example

Common pitfalls

Why it matters

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