I would like you to develop a new integration for me, but before we get started, I would like your assurance that my in-store inventory will be kept 100% accurate with my online inventory.
Let me rip the band-aid off quickly; it is impossible to ensure 100% accuracy between two disparate systems. I would also argue that it does not make sense to try to make it 100% accurate. Instead, it will probably be closer to 98% accurate, and that will likely work for you just fine. Let me explain.
Developers love to spend all their time on this 2%, and if we're not careful, it could occupy a substantial amount of time and money. Developers love talking about the 2% cases because they see it as a difficult engineering problem to solve – aka a "challenge." We could put a significant amount of time and money into worrying and trying to safeguard this 2%, but does it really justify the cost?
We have clients doing millions of dollars of business online a year, and in reality, they tell me they rarely have a problem with people buying out of stock merchandise. They say it may only happen once or twice a year. I would contend that you can handle this fringe case with good customer service.
Here’s a real world example I like. NASA spent $125 million on the Mars orbiter in the 90's. The orbiter was brilliant, and every system had two or three redundant systems in case the primary system failed. However, it crashed on the red planet. Why? Because one engineering team used Metric and the other team used English units. Oops.