Technical Debt & Sprint Velocity Simulator

Team & Process

Team size 6 devs

Feature pressure 60%

Refactor investment 20%

Test coverage discipline 50%

Sprint Readouts

Sprint #

Velocity

0.0 pts

Tech debt

0.0

Defect rate

0.0%

Features shipped

Bugs live

How it works

Each sprint, a team's raw capacity scales with headcount but is throttled by accumulated technical debt (Brooks's-law-style coordination overhead plus rework drag):

capacity = teamSize · basePts
velocity = capacity / (1 + debt / debtHalf)
shipped  = velocity · (pressure)  [story points]
debtGrowth = shipped · (1 − quality) − refactorRate · teamSize
debt(t+1)  = max(0, debt(t) + debtGrowth)
defectRate = f(1 − testCoverage, debt)  [bugs per shipped point]

Every point shipped without matching quality investment (refactor time, test coverage) adds to debt; debt then divides future velocity, so high-pressure/low-investment runs look fast for a few sprints and then stall — the classic "we shipped fast at first, now everything takes forever" curve. Refactor investment actively pays debt down instead of merely slowing its growth.

Feature pressure — fraction of raw capacity spent shipping new features vs. leaving slack.
Refactor investment — story points per developer per sprint spent paying down debt directly.
Test coverage discipline — reduces the defect rate for a given debt level and shipped volume.
The 3D tower's green layers are shipped features; the red haze is live tech debt; red sparks are open bugs.

Sprint 0 — press "Run Sprint"

Shipped feature block Open bug Debt haze

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