Kind-of-Lost

Three Bugs That Would Have Stayed Hidden in Excel

When you convert an optimization model from Excel to standalone Python, you expect to do some work. You expect to rewrite the data loading, restructure the variable definitions, test the output. What you don’t expect is for the model to fail in three distinct ways, each one caused by something the Excel version was handling silently without you knowing it.

That’s what happened here. Three bugs. All real. All the kind that would have stayed invisible forever if the model had stayed in the spreadsheet.

Why I switched to three billing cycles (and what it means if you want to sell tradelines too)

I’ve been selling authorized user tradelines for a few years now, and one thing I’ve been turning over in my head is the standard two-cycle product that most of the industry sells. Two billing cycles. Add the buyer, wait for two statement closes, remove them. That’s been the norm since before I got into this.

I’ve decided to move away from that. Going forward, every tradeline I sell — whether directly through this site or through the brokers I work with — runs for three billing cycles. Here’s why, and what it means if you’re thinking about either buying or selling tradelines.

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PuLP, MILP, and CBC: The Alphabet Soup Behind Your Schedule

PuLP is a Python library for writing optimization models. MILP stands for Mixed Integer Linear Program. CBC is an open-source solver. Together, they’re what makes the Staff Scheduler work — and together, they represent something I find genuinely interesting: the fact that problems that used to require expensive commercial software and specialized hardware can now be solved on a laptop, for free, in a few seconds.

Let me explain what’s actually happening under the hood.

Tradelines for Sale 2026

Every year around this time I get a wave of people asking whether tradelines are still worth buying. “Are they still working in 2026?” Short answer: yes. Longer answer: it depends on what you’re buying and who you’re buying from — and that part hasn’t changed since I started doing this.

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The Client Who Changed His Mind (And Why I Finished the Job Anyway)

Years ago, I was doing gigs on Fiverr. Mostly Excel work — macros, pivot tables, solver models. I had a profile and a handful of listings, and I’d written about that whole love/hate experience back in 2017 (short version: the clients who treat you like a vending machine are the price you pay for the ones who bring you genuinely interesting problems). One day, a genuinely interesting problem showed up.

A training company needed help scheduling their staff. Multiple clients, multiple courses, multiple instructors, limited hours, shared equipment, weird simultaneous constraints. Classic Operations Research territory. I said yes.

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