The speed that shows up in a sprint
A developer who works late can appear unusually productive: more features land, more bugs get patched, and deadlines are met. Caffeine can temporarily make someone feel more alert, helping them push through fatigue. But it does not replace sleep or restore every mental skill that tiredness erodes, such as sustained attention and careful judgment.
That matters because software work is not measured only by how many lines of code get written today. Code that is rushed, hard to read, or poorly documented can take longer for the same developer—or a teammate—to understand and change later.
When today's output becomes tomorrow's cost
Unreadable code and missing documentation create technical debt: future work becomes slower or riskier because earlier shortcuts must be untangled. A team may initially mistake one person's visible output for exceptional efficiency, while the costs surface later as confusing handoffs, fragile fixes, and time spent reconstructing how the system works.
The tradeoff is not simply that working late always produces bad software. Some intense pushes are necessary, and caffeine can help with short-term alertness. The problem is treating hours worked or tasks completed as the whole measure of performance. If speed depends on sacrificing rest and leaving work others cannot readily maintain, the apparent advantage may be borrowed from the team's future.
