24 Oct 2025

Back to the Future and the Mainframe That Forgot Its Timeline

By: Paco Campbell
Published: Friday, October 24th, 2025

It’s been forty years since Back to the Future hit theaters.
I didn’t rewatch it this week — I didn’t have to. The movie’s baked in by now: the DeLorean doors, the lightning strike, the hoverboard I begged Santa for multiple years in a row. Still waiting.

But the anniversary unearthed an old memory — the day I stumbled into my own time-travel paradox. No flux capacitor, just a mainframe, a CISO, and a few lines of config that shouldn’t have existed.

The Day the Mainframe Panicked

More than a decade ago, I was doing pre-sales architecture — the “help design it, pitch it, don’t touch production” kinda’ gig.

A customer’s mainframe suddenly went sideways. Rare event. Hard crash. The kind of thing that fills a war room before anyone knows what’s wrong.

And I just happened to be there.

When production breaks, proximity beats innocence.
That day, I was the closest warm body.

I’d never been yelled at professionally like that.
Didn’t write the code. Didn’t install the thing. Just happened to be standing near when it all came tumbling down.

The Printouts

Wanting to help (and clear my name), I asked the CISO if I could see the boot configuration the mainframe loaded on startup.

He smiled — politely dismissive — and a short while later handed me two thin printouts. Four pages each, maybe.

One from QA, where everything worked.
One from production, where the world had ended.

“They’re identical,” he said. “We have controls,” he finished, as he crossed his arms.

I felt like an idiot. Imposter syndrome? More like I’m just a kid trying to help and asked a C-level exec for a printout that he knows leads to nowhere and so he was playing good sport after chewing me earlier? (Kudos to you if you read that sentence in an agonizing and anxiety fueled one-breath pass. That’s exactly why the sentence is written to give all English majors a slight rash. Sorry!)

So I sat down with a highlighter and mild dread, scanning through hundreds of lines of assembly-meets-English syntax.

And three pages in, there it was.
Not one line — three.

Three entries pulling in (what I later learned was) a Computer Associates module that QA never loaded.

I highlighted them and walked back to his office.
He looked down, blinked, then went straight to his terminal — green-screen glow, the steady heartbeat of the cursor.

He checked. Verified. Then stared.

QA and prod weren’t identical.
Prod had drifted.

The Wrong Thing in the Wrong Timeline

The post-mortem confirmed it.
That CA module — authorized, elevated, perfectly legitimate — had tried to write into the memory space used by our Oracle component.

Oracle, running with system privileges, didn’t appreciate the intrusion.
Its watchdog process caught the access, flagged a memory violation, and the operating system did the only safe thing left: it ABENDed.

A clean, defensive self-termination.
Not an explosion — an airbag.

Not today, Satan, I imagine it would have said.

Mainframes are built for resilience, but they’re not unsinkable.
Two privileged modules colliding in protected memory can still punch a hole below the waterline.

Every Drift Is a Paradox

That CISO swore the configs were the same. He wasn’t lying.
He believed it.
Controls, governance, documentation — all perfectly reasonable faiths.

But belief doesn’t synchronize timelines.

QA was Hill Valley, 1955.
Production was the alternate 1985, Biff’s casino glittering where the courthouse used to be.
Everyone thought they were living in the same reality — until the photo started to fade.

So, AWS Sneezed…

Fast-forward to this week.
October 20. AWS had a widespread outage.

The culprit? DNS. (It’s always DNS).

Different decade, same movie.
A subtle misstep ripples through a web of dependencies, and suddenly the future collapses.

That’s the Marty McFly problem: one small change, and by the time you notice, you’re already disappearing.

Doc Brown Had It Coming

Doc Brown was a genius, but his security posture was a horror show.
Traded plutonium with Libyan terrorists. Gave a teenager the keys to spacetime. Wrote nothing down.

It wasn’t the science that nearly killed him — it was the assumptions.

That mainframe crash wasn’t malice or incompetence. It was misplaced faith: the idea that “identical” meant identical, that controls caught everything, that drift was impossible.

Every system is a timeline.
Every config file, a branching event.
Every untracked change, a trip through time you didn’t mean to take.

We think our systems are steady, but they’re really stitched together by trust and time.
Lose track of either, and you wake up in a future you don’t recognize.

Back to the Future (and Back to Work)

I didn’t fix that mainframe. I just found the paradox.
The CISO saw it for himself, and for a moment, you could see the realization click — that drift hides behind confidence.

That’s the real lesson.
It’s not about failure; it’s about entropy.

Cue Goldblum saying, “Life finds a way”.

Tiny differences creating massive consequences.

Forty years later, Back to the Future still nails it:
Timelines don’t collapse all at once. They drift, quietly, until someone notices the photo changing.

And sometimes, saving the future means catching three stray lines on a four-page printout.

Great Scott.