The Skylight Bug
Early in my career we built digital signs for retail stores—solid hardware, clean code, perfect test results.
Then one location started failing every afternoon at three o’clock.
Same code. Same network. Same everything.
We tore through logs for days. Nothing.
Finally, someone flew out and saw it in person.
A skylight was focusing a beam of sunlight directly onto the unit each afternoon.
The system wasn’t crashing—it was cooking.
No remote debug would ever have found that.
The issue wasn’t in the code; it was in the assumption that code was the whole system.
Reality had extra variables—heat, light, time—that didn’t exist in our telemetry.
That was the day I stopped thinking like a developer and started thinking like an engineer.
Looking Beyond the Obvious
The store employees never mentioned the skylight because it had always been there.
To them it was part of the scenery, not part of the problem.
That’s how most investors treat markets: they analyze the visible variables—price, yield, charts—but ignore the skylights overhead.
Policy shifts. Tax timing. Liquidity droughts.
Thinking like an engineer means noticing what everyone else filters out.
If something can heat your system, it matters, even if it’s been there forever.
QA Logic for a Chaotic World
In software, good QA doesn’t test what’s supposed to happen.
They test what should never happen.
They order 999,999 beers.
They order -1 beer.
They type “asfjskflsjf” into the quantity box.
And the system still has to handle it gracefully.
Markets are the same.
They’re the ultimate QA team—throwing malformed input at your portfolio all day long: inflation spikes, flash crashes, rate shocks, Reddit mobs.
A trader says, “If I just had enough data, I could predict it.”
An engineer says, “I can’t predict it, but I can design a system that survives it.”
The 2× Rule (and the Real Engineers Who Invented It)
NASA pioneered what engineers now call the 2× Rule:
design every mission-critical component to tolerate at least twice the expected stress.
If a capsule re-entry computer had to endure 200 °C, they built it for 400.
If a signal needed one radio, they launched with two—and sometimes a third, wired for cross-check.
That mindset wasn’t born in Houston; it came from John von Neumann, the mathematician who first imagined fault-tolerant computing.
His idea was simple but radical: run three separate processors on the same calculation and only trust the answer if all three agree.
That’s how modern spacecraft, aircraft, and even your phone’s autopilot logic stay alive when one chip glitches.
Finance deserves the same respect for physics.
If you need $3 000 a month to live, build for $6 000.
Not because you’ll spend it, but because the world will always run hotter than the spec sheet.
That redundancy buys you time to think instead of react—and time is the rarest safety feature there is.
Graceful Failure Modes
Every engineer knows perfection doesn’t exist; only failure modes do.
What separates a panic from a recovery is grace.
We hide loading time behind animations so users feel flow, not lag.
We put a logo screen behind every UI element so that if the whole system explodes, there’s still something on-brand on the display.
That “something” also helps us debug—the layer that survives tells us which subsystem died first.
Your portfolio needs the same tricks.
When an ETF stalls, another keeps paying.
When volatility melts the high-yield core, the shell vents pressure.
If everything fails at once, the safety screen is cashflow itself—it keeps the user (you) calm long enough to fix what broke.
Graceful failure doesn’t mean nothing breaks.
It means the system fails in a way that preserves information and dignity.
That’s how you build software that stays online—and portfolios that keep earning—through skylights, storms, and every absurd QA test the universe can throw at them.
You can always reach me at [email protected] if you want to go deeper.
Disclaimer: This post is for informational purposes only and reflects personal opinions, not financial advice. Oppenfolio is not an investment advisory service. See site disclaimer for full details.