- Waterfall is a linear, phase-gated software delivery model where work flows downward through fixed stages, and each stage must be completed before the next begins.
- It was designed for predictability, not speed.
Definition
- Waterfall is a sequential software delivery model where each phase is completed once, changes are costly, and feedback arrives late.
The Waterfall Phases
Requirements
↓
Design
↓
Development
↓
Testing
↓
Deployment
↓
Maintenance
Each phase is:
- Completed once
- Signed off
- Locked before moving forward
No looping back without formal change requests.
Why Waterfall Made Sense (Historically)
Waterfall worked well when:
- Software requirements were stable
- Releases were rare
- Systems were simple
- Hardware was expensive
- Changes were risky
Industries like:
- Government
- Banking
- Defense
- Telecom
used it heavily because control and documentation mattered more than speed.
How Work Actually Happened
Requirements
- Business wrote large requirement documents
- Assumed full clarity upfront
- Changes were discouraged
Design
- Architects produced detailed designs
- Decisions were frozen early
- Future assumptions were baked in
Development
- Dev implemented based on specs
- Minimal user feedback
- Problems surfaced late
Testing
- Testing happened near the end
- Bug fixes were expensive
- Time pressure was extreme
Deployment
- Manual, risky
- Often after months or years
- Rollbacks were painful
Core Characteristics
| Aspect | Waterfall |
|---|---|
| Flow | Linear |
| Feedback | Late |
| Change cost | High |
| Release size | Large |
| Risk discovery | End of cycle |
| Automation | Minimal |
Why Waterfall Fails for Modern Software
1️⃣ Assumes Requirements Will Not Change
They always do.
2️⃣ Delays Feedback
Bugs and design flaws appear too late.
3️⃣ Encourages Big Bang Releases
Large blast radius, hard rollback.
4️⃣ Separates Builders from Operators
Developers rarely see production issues.
5️⃣ Optimizes for Documentation Over Outcomes
You can follow the process and still fail users.
Relationship to DevOps
Waterfall is not evil. It is misused.
Problems arose when:
- Waterfall delivery
- Plus functional silos
- Plus manual operations
- Plus frequent business change
DevOps emerged to fix what Waterfall could not:
- Continuous feedback
- Automation
- Shared ownership
The Harsh Truth.
Waterfall fails not because people are bad, but because it assumes certainty in a world that is uncertain.
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