Many ages ago, at my first software engineering job, I was tasked with building a new replacement system for an aging platform. I decided to write this in the new-thing at the time, C# and .Net.

I managed to put together the overall framework, architect a SQL database for it, and after a bit of time had a working replacement for the most important parts of what it was replacing. While discussing the next steps, the owner of the company mentions he just sold one already to one of the largest clients using the old system. I found that rather surprising, as he made no mention of announcing it let alone starting to sell it, and it wasn't ready to be sold, but here we were.

We go to meet with this company to discuss specifics, and one of the questions they ask is "exactly how much bandwidth is utilized when we do X? We have Y employees and want to know exactly how much it uses if they were to be using it at the same time".

Now, I wrote this thing to be as performant as I could, but at no point up to now did I have time to run specific performance metrics on it such as how much bandwidth was being used by every specific piece of functionality. It wasn't even an announced product, as far as I knew.

My boss turns and just stares at me. So I answered honestly, said I didn't have the exact numbers, and I can get back to them, but I felt that their current setup should be more than sufficient.

Meeting ends, we get back to the car, and he is suddenly irate.

"Don't ever, ever tell a client you don't know something! How could you do that? That made us look like we don't even understand our own product! You know what you do in that situation? Make up a number that works! You never say you don't know! Unbelievable!"

I'm not in sales. I got dragged into this meeting out of nowhere only to get chewed out for not properly fielding a question, about a product that I didn't know we were selling, that I couldn't possibly have expected to answer at that point.